H
Articles written in Pramana – Journal of Physics
Volume 3 Issue 4 October 1974 pp 236-242 Atmospheric Physics
Equatorial
The times of reversal of east-west electrostatic field in the ionosphere near the equator in the Indian zone have been estimated from the measurements of ionospheric drift at Thumba. The reversal of electric field in the morning from westward to eastward is delayed with respect to the sunrise at 100 km by 1.5 hr during winter and by about 3 hr during summer months. The reversal in the evening from eastward to westward occurs around 2100 hrs,
Volume 3 Issue 5 November 1974 pp 277-285 Solids
Topotaxy in the oxidation of valentinite, Sb_{2}O_{3}, to cervantite, Sb_{2}O_{4}
The oxidation of orthorhombic Sb_{2}O_{3}, valentinite, to orthorhombic Sb_{2}O_{4}, cervantite, has been shown by single crystal x-ray diffraction techniques to be a topotactic reaction. The orientation relationships between the two lattices have been determined by making use of a hybrid crystal. It has been found that the individual axes in the two oxides are parallel. The two crystal structures have been compared in the appropriate orientation and their close similarity has been established. The shifts of the individual atoms in valentinite during the process of oxidation have been calculated to be not more than 0·6 Å. It has been established that the reduction of cervantite to valentinite also takes place topotactically.
Volume 10 Issue 3 March 1978 pp 289-302 Experimental Techniques And Instrumentation
An on-line TDC-312 computer-controlled neutron diffractometer
A Sequeira S N Momin H Rajagopal J N Soni R Chidambaram Dilip Kumar A Ramana Rao V M Gopu
The design and fabrication of an indigenous on-line computer controlled four-circle neutron diffractometer at the CIRUS reactor in Trombay are described. The diffractometer has an 18 in dia full-circle crystal-orienter which is sturdy enough to carry a cryostat. Three crystal orientation angles χ, φ and ω and the detector angle 2θ can be set to an accuracy of 0·01°. The four angle shafts are driven through precision worm-gears by SCR-controlled DC motors and their instantaneous positions sensed by optical digitizers. The diffractometer is interfaced to an ECIL TDC-312 computer system consisting of the CPU with 4K-memory, ASR-35 teletype, X-Y plotter and the digital input/output system (DIOS). The DIOS which operates under program control is a real-time peripheral device used to exchange information in digital form between the computer and the diffractometer. A software package consisting of over 40 useroriented teletype commands has been developed for on-line control and automatic data-acquisition.
Volume 14 Issue 1 January 1980 pp 57-74 Nuclear And Particle Physics
$${}_{\Lambda \Lambda }^{10} Be$$ in Faddeev-Yakubovsky formalismin Faddeev-Yakubovsky formalism
H Roy-Choudhury V P Gautam D P Sural
The four-body dynamical equations for two distinct pairs of identical particles derived earlier are applied to investigate the system$${}_{\Lambda \Lambda }^{10} Be$$. The two-body potentials have been taken to be of the Yamaguchi form, and the Bateman approximation has been used for the other amplitudes. From the set of coupled integral equations, the separation energy, B_{ΛΛ}, for the two Λ particles in$${}_{\Lambda \Lambda }^{10} Be$$ is obtained as 43·97 MeV.
Volume 14 Issue 5 May 1980 pp 349-362 Instrumentation
H Heck I S Williams E S R Gopal S Jyothi
The design and construction of precision temperature controllers, capable of tracking the temperature of the samples to within 1 mK for ramp heating rates from 0.05 to 10 K per hour, are discussed. A tutorial section on the evolution of the control loop configuration is first given. This is followed by an outline of the refinements of the basic control loop desirable in the actual implementation of the electronic controller. The novel features of the present system and its performance are then briefly discussed. Finally the inadequacy of the conventional PID controllers for this application, the estimation of the time constants of the physical system needed in the design of the electronic controllers and the pitfalls in using a simple model of the heater plus thermometer assembly with a single pole are also discussed.
Volume 25 Issue 4 October 1985 pp 383-395 Quantum Statistics
The neutron interferometer as a macroscopic quantum device
Neutron interferometry is a unique tool for investigations in the field of particle-wave dualism because massive elementary particles behave like waves within the interferometer. The invention of perfect crystal neutron interferometers providing widely separated coherent beams stimulated a great variety of experiments with matter waves in the field of basic quantum mechanics. The phase of the spatial and spinor wave function become a measurable quantity and can be influenced individually. High degrees of coherence and high order interferences have been observed by this technique. The 4π-symmetry of a spinor wave function and the mutual modulation of nuclear and magnetic phase shifts have been measured in the past. Recent experiments dealt with polarized neutron beams, which are handled to realize the spin-superposition of two oppositionally polarized subbeams resulting in a final polarization perpendicular to both initial beam polarizations. The different actions on the coherent beams of static (DC) and dynamic (HF) flippers have been visualized.
Volume 28 Issue 1 January 1987 pp 59-71 Spectroscopy
Transient excited singlet state absorption in Rhodamine 6G
Putcha Venkateswarlu M C George Yerneni V Rao H Jagannath G Chakrapani A Miahnahri
Transient excited singlet state absorption (ESSA) has been studied in Rhodamine 6G in ethanol using a nitrogen laser and nitrogen laser-pumped dye laser. Broad absorption with several submaxima and possible shoulders, which represent the vibrational structure, has been observed in Rhodamine 6G in the region, 4175–4640 Å. The position of the lowest vibrational level of the first excited singlet state
Volume 36 Issue 2 February 1991 pp 207-219
Point contact tunnelling studies on ceramic YBCO with scanning tunnelling microscope tips
H Srikanth M Rajeswari A K Raychaudhuri
A detailed study of point contact tunnelling into ceramic YBCO with electrochemically etched tips of Pt, Nb and W is reported. The superconducting gap parameter (Δ) has been extracted from
Volume 36 Issue 6 June 1991 pp 621-627
By making a combination of both point contact and barrier type tunnel junctions on a single sample of the high
Volume 37 Issue 1 July 1991 pp 59-70
A nonperturbative variational approach to the vacuum structure in quantum chromodynamics
A Mishra H Mishra S P Misra S N Nayak
We study the vacuum structure in QCD in a nonperturbative manner using a variational approach with gluon condensates. We show that in Coulomb gauge as the coupling becomes moderately strong, the perturbative vacuum of QCD becomes unstable leading to gluon condensates and a gauge dependent effective mass for the gluons related to the gauge independent value of 〈vac‖
Volume 37 Issue 2 August 1991 pp 105-114
Application of a radioactive tracer method for diffusion study in some liquids
In this paper a radioactive tracer technique based on sliding cell method developed in our laboratory for the study of diffusion in liquids is presented in detail. This method consists of radioactive and non-radioactive liquid columns of equal length and the radiation detector is placed in a vertical geometry over the diffusion column. Some liquid metals and aqueous electrolyte solutions were studied by this method. The data of liquid metals like mercury and gallium have been analyzed from the point of view of hard sphere model and those of electrolyte solutions from phenomenological theories. Onsager’s coefficients
Volume 49 Issue 4 October 1997 pp 431-442 Research Articles
Electromagnetic properties of a chiral-plasma medium
H Torres-Silva C Villarroel P H Sakanaka N Reggiani
The theoretical properties of a composite chiral-plasma medium are developed. By using the reaction theorem for a magnetized chiroplasma, we obtain the proof of nonreciprocity based upon the constitutive relationships between electromagnetic vectors
Volume 53 Issue 3 September 1999 pp 609-618 Nuclei Act Extreme Conditions
Mass measurements of relativistic projectile fragments in the storage ring ESR
T Radon H Geissel F Attallah K Beckert F Bosch A Dolinskiy H Eickhoff M Falch B Franczak B Franzke Y Fujita M Hausmann M Hellström F Herfurth Th Kerscher O Klepper H-J Kluge C Kozhuharov Yu Litvinov KEG Löbner G Münzenberg F Nolden Yu Novikov Z Patyk W Quint H Reich C Scheidenberger B Schlitt J Stadlmann M Steck K Sümmerer L Vermeeren M Winkler Th Winkler H Wollnik
Two experimental methods of measuring masses of exotic nuclei in the storage ring ESR are presented. Bismuth and nickel fragments were produced via projectile fragmentation, separated and investigated with the combination of the fragment separator FRS and the ESR: (i) Direct mass measurements of relativistic projectile fragments were performed using Schottky mass spectrometry (SMS), i.e., exotic nuclei were stored and cooled in the ESR. Applying electron cooling, the relative velocity spread of circulating low intensity beams can be reduced below 10^{−6}. Under this condition a mass resolving power of up to
Volume 55 Issue 1-2 July 2000 pp 195-205
Experimental status of
In a short period of time, we will have a large amount of results from
Volume 55 Issue 1-2 July 2000 pp 335-345
Debajyoti Choudhury Rahul Sinha S Arunagiri Gautam Bhattacharyya Debrupa Chakraverty Debajyoti Choudhury Amitava Datta Anindya Datta Aseskrishna Datta Amol Dighe Dilip Kumar Ghosh Anjan Giri Stephen King Anirban Kundu Rukmani Mohanta Biswarup Mukhopadhyaya Sreerup Raychaudhuri Saurabh Rindani Probir Roy DP Roy Sourov Roy AI Sanda Nita Sinha Rahul Sinha K Sridhar H Yamamoto
This report summarises the work done during WHEPP-6 (Institute of Mathematical Sciences, Chennai, India, Jan 3–15, 2000) in Working group on ‘
Volume 55 Issue 5-6 November 2000 pp 757-771 Laser Plasmas, Invited Talks
D Subbarao R Uma H Singh Kamal Goyal Sanjeev Goyal Ravinder Kumar
It is useful to state propagation laws for a self-focusing laser beam or a soliton in group-theoretical form to be called Lie-optical form for being able to predict self-focusing dynamics conveniently and amongst other things, the geometrical phase. It is shown that the propagation of the gaussian laser beam is governed by a rotation group in a non-absorbing medium and by the Lorentz group in an absorbing medium if the additional symmetry of paraxial propagation is imposed on the laser beam. This latter symmetry, however, needs care in its implementation because the electromagnetic wave of the laser sees a different refractive index profile than the laboratory observer in this approximation. It is explained how to estimate this non-Taylor paraxial power series approximation. The group theoretical laws so-stated are used to predict the geometrical or Berry phase of the laser beam by a technique developed by one of us elsewhere. The group-theoretical Lie-optic (or ABCD) laws are also useful in predicting the laser behavior in a more complex optical arrangement like in a laser cavity etc. The nonlinear dynamical consequences of these laws for long distance (or time) predictions are also dealt with. Ergodic dynamics of an ensemble of laser beams on the torus during absorptionless self-focusing is discussed in this context. From the point of view of new physics concepts, we introduce a stroboscopic invariant torus and a stroboscopic generating function in classical mechanics that is useful for long-distance predictions of absorptionless self-focusing.
Volume 55 Issue 5-6 November 2000 pp 887-898 Plasma Processes, Contributed Papers
A self-consistent kinetic modeling of a 1-D, bounded, plasma in equilibrium
Monojoy Goswami H Ramachandran
A self-consistent kinetic treatment is presented here, where the Boltzmann equation is solved for a particle conserving Krook collision operator. The resulting equations have been implemented numerically. The treatment solves for the entire quasineutral column, making no assumptions about λ_{mfp}/
Volume 56 Issue 2-3 February 2001 pp 349-355 Quantum Information Processing
Causality, relativity and quantum correlation experiments with moving reference frames
H Zbinden J Brendel W Tittel N Gisin
Entanglement, one of the most important features of quantum mechanics, is at the core of the famous Einstein-Bohr philosophical debate [1] and is the principal resource for quantum information processing [2]. We report on new experimental investigations of the properties of entangled photon pairs with emphasis on the tension between quantum mechanics and relativity [3,4]. Entangled photons are sent via an optical fiber network to two villages near Geneva, separated by more than 10 km where they are analyzed by interferometers [5]. The photon pair source is set as precisely as possible in the center so that the two photons arrive at the detectors within a time interval of less than 5 ps (corresponding to a path length difference of less than 1 mm). This sets a lower bound on the ‘speed of quantum information’ to 10^{7} times the speed of light. Next, one detector is set in motion [6] so that both detectors, each in its own inertial reference frame, are first to do the measurement! The data always reproduces the quantum correlations.
Volume 57 Issue 1 July 2001 pp 161-164 Contributed Papers, Nuclear Spectroscopy
Gamma-ray spectroscopy with relativistic exotic heavy-ions
Samit Mandal J Gerl H Geissel K Hauschild M Hellström Z Janas I Kojouharov Y Kopatch RC Lemmon P Mayet Z Podolyak PH Regan H Schaffner C Schlegel J Simpson HJ Wollersheim
Feasibility of gamma-ray spectroscopy at relativistic energies with exotic heavy-ions and new generation of germanium detectors (segmented Clover) is discussed. An experiment with such detector array and radioactive is discussed.
Volume 57 Issue 1 July 2001 pp 195-198 Contributed Papers, Nuclear Reactions
Fusion around the barrier for ^{7}Li+^{12}C
A Mukherjee M Dasgupta DJ Hinde CR Morton AC Berriman RD Butt JO Newton H Timmers
Fusion cross-sections for the ^{7}Li + ^{12}C reaction have been measured at energies above the Coulomb barrier by the direct detection of evaporation residues. The heavy evaporation residues with energies below 3 MeV could not be separated out from the α-particles in the spectrum and hence their contribution was estimated using statistical model calculations. The present work indicates that suppression of fusion cross-sections due to the breakup of ^{7}Li may not be significant for ^{7}Li + ^{12}C reaction at energies around the barrier.
Volume 57 Issue 2-3 August 2001 pp 285-300
Multiplicity distributions and charged-neutral fluctuations
Tapan K Nayak MM Aggarwal A Agnihotri Z Ahammed ALS Angelis V Antonenko V Arefiev V Astakhov V Avdeitchikov TC Awes PVKS Baba SK Badyal A Baldine L Barabach C Barlag S Bathe B Batiounia T Bernier KB Bhalla VS Bhatia C Blume R Bock E-M Bohne D Bucher A Buijs E-J Buis H Büsching L Carlen V Chalyshev S Chattopadhyay KE Chenawi R Cherbatchev T Chujo A Claussen AC Das MP Decowski V Djordjadze P Donni I Doubovik AK Dubey MR Dutta Majumdar S Eliseev K Enosawa H Feldmann P Foka S Fokin V Frolov MS Ganti S Garpman O Gavrishchuk FJM Geurts TK Ghosh R Glasow SK Gupta B Guskov HA Gustafsson HH Gutbrod R Higuchi I Hrivanacova M Ippolitov H Kalechofsky R Kamermans K-H Kampert K Karadjev K Karpio S Kato S Kees H Kim BW Kolb I Kosarev I Koutcheryaev A Kugler P Kulinich V Kumar M Kurata K Kurita N Kuzmin I Langbein A Lebedev YY Lee H Löhner DP Mahapatra V Manko M Martin A Maximov R Mehdiyev G Mgebrichvili Y Miake D Mikhalev GC Mishra Y Miyamoto B Mohanty D Morrison DS Mukhopadhyay V Myalkovski H Naef BK Nandi SK Nayak TK Nayak S Neumaier A Nianine V Nikitine S Nikolaev S Nishimura P Nomokov J Nystrand FE Obenshain A Oskarsson I Otterlund M Pachr A Parfenov S Pavliouk T Peitzmann V Petracek F Plasil ML Purschke B Raeven J Rak R Raniwala S Raniwala VS Ramamurthy NK Rao F Retiere K Reygers G Roland L Rosselet I Roufanov JM Rubio SS Sambyal R Santo S Sato H Schlagheck H-R Schmidt G Shabratova I Sibiriak T Siemiarczuk BC Sinha N Slavine K Söderström N Solomey G Sood SP Sørensen P Stankus G Stefanek P Steinberg E Stenlund D Stüken M Sumbera T Svensson MD Trivedi A Tsvetkov C Twenhöfel L Tykarski J Urbahn NV Eijndhoven WHV Heeringen GJV Nieuwenhuizen A Vinogradov YP Viyogi A Vodopianov S Vörös MA Vos B Wyslouch K Yagi Y Yokota GR Young
Results from the multiplicity distributions of inclusive photons and charged particles, scaling of particle multiplicities, event-by-event multiplicity fluctuations, and charged-neutral fluctuations in 158
Volume 57 Issue 2-3 August 2001 pp 355-369
First results from RHIC-PHENIX
Tarun Kanti Ghosh K Adcox S S Adler N Ajitanand Y Akiba J Alexander L Aphecetche Y Arai S H Aronson R Averbeck T C Awes K N Barish P D Barnes J Barrette B Bassalleck S Bathe V Baublis A Bazilevsky S Belikov F G Bellaiche S T Belyaev M J Bennett Y Berdnikov S Botelho M L Brooks D S Brown N Bruner D Bucher H Buesching V Bumazhnov G Bunce J Burward-Hoy S Butsyk T A Carey P Chand J Chang W C Chang L L Chavez S Chernichenko C Y Chi J Chiba M Chiu R K Choudhury T Christ T Chujo M S Chung P Chung V Cianciolo B A Cole D G D’Enterria G David H Delagrange A Denisov A Deshpande E J Desmond O Dietzsch B V Dinesh A Drees A Durum D Dutta K Ebisu Y V Efremenko K El Chenawi H En’yo S Esumi L Ewell T Ferdousi D E Fields S L Fokin Z Fraenkel A Franz A D Frawley S-Y Fung S Garpman T K Ghosh A Glenn A L Godoi Y Goto S V Greene M Grosse Perdekamp S K Gupta W Guryn H-Å Gustafsson J S Haggerty H Hamagaki A G Hansen H Hara E P Hartouni R Hayano N Hayashi X He T K Hemmick J Heuser J C Hill D S Ho K Homma B Hong A Hoover T Ichihara K Imai M S Ippolitov M Ishihara B V Jacak W Y Jang J Jia B M Johnson S C Johnson K S Joo S Kametani J H Kang M Kann S S Kapoor S Kelly B Khachaturov A Khanzadeev J Kikuchi D J Kim H J Kim S Y Kim Y G Kim W W Kinnison E Kistenev A Kiyomichi C Klein-Boesing S Klinksiek L Kochenda D Kochetkov V Kochetkov D Koehler T Kohama A Kozlov P J Kroon K Kurita M J Kweon Y Kwon G S Kyle R Lacey J G Lajoie J Lauret A Lebedev D M Lee M J Leitch X H Li Z Li D J Lim M X Liu X Liu Z Liu C F Maguire J Mahon Y I Makdisi V I Manko Y Mao S K Mark S Markacs G Martinez M D Marx A Masaike F Matathias T Matsumoto P L McGaughey E Melnikov M Merschmeier F Messer M Messer Y Miake T E Miller A Milov S Mioduszewski R E Mischke G C Mishra J T Mitchell A K Mohanty D P Morrison J M Moss F Mühlbacher M Muniruzzaman J Murata S Nagamiya Y Nagasaka J L Nagle Y Nakada B K Nandi J Newby L Nikkinen P Nilsson S Nishimura A S Nyanin J Nystrand E O’Brien C A Ogilvie H Ohnishi I D Ojha M Ono V Onuchin A Oskarsson L Österman I Otterlund K Oyama L Paffrath A P T Palounek V S Pantuev V Papavassiliou S F Pate T Peitzmann A N Petridis C Pinkenburg R P Pisani P Pitukhin F Plasil M Pollack K Pope M L Purschke I Ravinovich K F Read K Reygers V Riabov Y Riabov M Rosati A A Rose S S Ryu N Saito A Sakaguchi T Sakaguchi H Sako T Sakuma V Samsonov T C Sangster R Santo H D Sato S Sato S Sawada B R Schlei Y Schutz V Semenov R Seto T K Shea I Shein T-A Shibata K Shigaki T Shiina Y H Shin I G Sibiriak D Silvermyr K S Sim J Simon-Gillo C P Singh V Singh M Sivertz A Soldatov R A Soltz S Sorensen P W Stankus N Starinsky P Steinberg E Stenlund A Ster S P Stoll M Sugioka T Sugitate J P Sullivan Y Sumi Z Sun M Suzuki E M Takagui A Taketani M Tamai K H Tanaka Y Tanaka E Taniguchi M J Tannenbaum J Thomas J H Thomas T L Thomas W Tian J Tojo H Torii R S Towell I Tserruya H Tsuruoka A A Tsvetkov S K Tuli H Tydesjö N Tyurin T Ushiroda H W van Hecke C Velissaris J Velkovska M Velkovsky A A Vinogradov M A Volkov A Vorobyov E Vznuzdaev H Wang Y Watanabe S N White C Witzig F K Wohn C L Woody W Xie K Yagi S Yokkaichi G R Young I E Yushmanov W A Zajc Z Zhang S Zhou
The PHENIX experiment consists of a large detector system located at the newly commissioned relativistic heavy ion collider (RHIC) at the Brookhaven National Laboratory. The primary goal of the PHENIX experiment is to look for signatures of the QCD prediction of a deconfined high-energy-density phase of nuclear matter quark gluon plasma. PHENIX started data taking for Au+Au collisions at √
Volume 57 Issue 2-3 August 2001 pp 371-377
Nuclear responses for neutrinos and neutrino studies by double beta decays and inverse beta decays
This is a brief report on recent studies of nuclear responses for neutrinos (
Volume 57 Issue 2-3 August 2001 pp 399-416
Meson production in
H Machner M Betigeri J Bojowald A Budzanowski A Chatterjee J Ernst L Freindl D Frekers W Garske K Grewer A Hamacher J Ilieva L Jarczyk K Kilian S Kliczewski W Klimala D Kolev T Kutsarova J Lieb H Machner A Magiera H Nann L Pentchev HS Plendl D Protić B Razen P Von Rossen BJ Roy R Siudak J Smyrski RV Srikantiah A Strzałkowski R Tsenov K Zwoll
Total and differential cross sections for the reactions
Volume 57 Issue 2-3 August 2001 pp 417-431
Chiral unitary theory: Application to nuclear problems
E Oset D Cabrera H C Chiang C Garcia Recio S Hirenzaki S S Kamalov J Nieves Y Okumura A Ramos H Toki M J Vicente Vacas
In this talk we briefly describe some basic elements of chiral perturbation theory,
Volume 57 Issue 2-3 August 2001 pp 535-544
Structure of light neutron-rich nuclei through coulomb dissociation
U Datta Pramanik T Aumann D Cortina H Emling H Geissel M Hellström R Holzmann N Iwasa Y Leifels G Münzenberg M Rejmund C Scheidenberger K Sümmerer A Leistenschneider Th W Elze A Grünschloss S Ilievski K Boretzky J V Kratz R Kulessa E Lubkiewicz E Wajda W Walus P Reiter H Simon
Coulomb breakup of neutron-rich nuclei around mass
Volume 57 Issue 2-3 August 2001 pp 665-670
This is a brief summary of the ISNP2K (International Symposium on Nuclear Physics, 2000). Many interesting works were presented on new developments and perspectives of nuclear physics in the plenary and poster sessions. Subjects discussed are 1) high temperature and high density nuclei, new QGP phases and relativistic HI collisions, 2) new degrees of freedoms studied by medium energy reactions, 3) exotic nuclei with large isospin, large
Volume 58 Issue 5-6 May 2002 pp 715-723 Strongly Correlated Electron Systems
Magnetotransport of the low-carrier density one-dimensional
P Gegenwart H Aoki T Cichorek J Custers M Jaime A Ochiai F Steglich
The transport properties of the semimetallic quasi-one-dimensional
Volume 58 Issue 5-6 May 2002 pp 737-742 Strongly Correlated Electron Systems
Local-moment formation and metal-nonmetal transition in Ca_{1−x}Y_{x}VO_{3} and Ca_{1−x}Y_{x}TiO_{3}
Y Nishihara H Kawanaka H Bando
Electron-doped metallic states of Ca_{1−x}Y_{x}VO_{3} and Ca_{1−x}Y_{x}TiO_{3} change into non-metallic states around
Volume 58 Issue 5-6 May 2002 pp 743-754 Strongly Correlated Electron Systems
Metals near a magnetic instability
H v Löhneysen C Pfleiderer A Schröder O Stockert
Zero-temperature magnetic phase transitions exhibit an abundance of nearly critical magnetic fluctuations that allow to probe the traditional concepts of the metallic state. For the prototypical heavy-fermion compound, CeCu_{6−x}Au_{x}, a breakdown of the Fermi-liquid properties may be tuned by Au concentration, hydrostatic pressure, or magnetic field. The d-electron weak itinerant ferromagnet ZrZn_{2}, on the other hand, was recently found to display superconductivity in coexistence with ferromagnetism.
Volume 58 Issue 5-6 May 2002 pp 777-782 Strongly Correlated Electron Systems
Spin-glass, antiferromagnetism and kondo behavior in Ce_{2}Au_{1−x}Co_{x}Si_{3} alloys
Subham Majumdar EV Sampathkumaran St Berger M Della Mea H Michor E Bauer M Brando J Hemberger A Loidl
Recently, the solid solution Ce_{2}Au_{1−}_{x}_{Co}
Volume 58 Issue 5-6 May 2002 pp 809-815 Superconductivity
VPS Awana M Karppinen H Yamauchi
Both RuSr_{2}GdCu_{2}O_{8-δ} (Ru-1212) and RuSr_{2}Gd_{1.5}Ce_{0.5}Cu_{2}O_{10-δ} (Ru-1222) exhibits magnetism and superconductivity, as seen by magnetization vs. temperature behavior measured in 5 Oe field. Zero-field-cooled (ZFC) and field-cooled (FC) magnetization data show branching at around 140 K and 100 K with a cusp at 135 K and 80 K and a diamagnetic transition around 20 K and 30 K in the ZFC part, for Ru-1212 and Ru-1222, respectively. The isothermal magnetization possesses a non-linear contribution due to a ferromagnetic component at low temperatures below 50 K for both samples. The resistance vs. temperature behavior of the samples in applied fields of 0, 3 and 7 T confirmed superconductivity, with a different type of broadening of the superconductivity transition under magnetic fields for Ru-1212 from that known for conventional high-
Volume 58 Issue 5-6 May 2002 pp 919-924 Physics Of Vortex State
Commensurability oscillations in NdBa_{2}Cu_{3}O_{y} single crystals
H Küpfer G Ravikumar Th Wolf AA Zhukov H Wühl
Commensurability between inter-vortex distance and crystal lattice constant is investigated by angular dependent magnetization in very pure twinned and twin-free NdBa_{2} Cu_{3} O_{y} single crystals. With increasing temperature the incommensurate states split up and become finally commensurate with half the vortex distance. These new commensurate states are related to a substructure of the intrinsic pinning potential within the unit cell and discussed with respect to temperature, field, anisotropy, and twin structure.
Volume 59 Issue 6 December 2002 pp 915-921
MAFF — The Munich accelerator for fission fragments
L Beck D Habs P Reiter P Thirolf T Sieber H Bongers S Emhofer H J Maier
At the new high flux reactor FRM-II in Munich the accelerator MAFF (Munich accelerator for fission fragments) is under design. In the high neutron flux of 10^{14} n/cm^{2} s up to 10^{14} neutron-rich fission fragments per second are produced in the 1 g U-235 target. Ions with an energy of 30 keV are extracted from the ion source. In the mass separator two isotopes can be selected. One of the beams is used for low energy experiments, the other one is injected into an ECRIS (or EBIS) for charge breeding to a
Volume 59 Issue 6 December 2002 pp 957-962
The design of a radio frequency quadrupole LINAC for the RIB project at VECC Kolkata
V Banerjee Alok Chakrabarti Arup Bandyopadhyay T K Bhaumik M Mondal T K Chakraborty H Pande O Kamigaito A Goto Y Yano
A radio frequency quadrupole LINAC has been designed for the VECC-RIB project for an input beam energy of 1.0 keV/u and
Volume 62 Issue 1 January 2004 pp 37-52
Non-linear polarization and chiral effects in birefringent solitons
H Torres-Silva M Zamorano Lucero
Novel effects resulting from joint action of chirality and non-linearity are discussed using a basic equation describing the temporal evolution of fields in a chiral medium with Kerr non-linearity. The spatial chirality effect is characterized through the Born-Fedorov formalism. Our simulations are based on the split-step Fourier method and the solution of the Stokes parameters. The numerical results show the chiral effect on solitons with circular polarization and mixed polarization spatial solitons.
Volume 62 Issue 1 January 2004 pp 53-60
Optimization and performance of a high-speed plasma position digital control system
M Emami A R Babazadeh H Rasouli
This paper addresses optimization of a high-speed digital feedback controller for a plasma position in Damavand tokamak. Damavand tokamak discharges have plasma currents up to 40 kA with discharge duration greater than 15 ms and toroidal magnetic fields up to 1.2 T. The plasma position is measured using saddle-loops and Rogowski coil and is controlled by electromagnetic forces generated by passing currents through control coils placed around the plasma. A desired control objective is maintaining the plasma in the center of vacuum vessel and to stabilize the plasma in the presence of disturbances in a time domain of the order of few milliseconds. In order to achieve maximum performance it is essential to optimize the control system. In this paper plasma position measurement and the details of implementing high-speed PID controllers based on a TMS320c25 digital signal processor along with the system optimization are presented.
Volume 62 Issue 1 January 2004 pp 77-86
H Anandalakshmi K Velavan I Sougandi R Venkatesan P Sambasiva Rao
Single crystal EPR studies of Mn(II)-doped zinc ammonium phosphate hexahydrate (ZnNH_{4}PC_{4}·6H_{2}O) have been reinvestigated at room temperature. Single crystal rotations along the three orthogonal axes indicate that the spin Hamiltonian parameters for the interstitial site are:
Volume 67 Issue 1 July 2006 pp 199-205
G H Döhler M Eckardt A Schwanhäußer F Renner S Malzer S Trumm M Betz F Sotier A Leitenstorfer G Loata T Löffler H Roskos T Müller K Unterrainer D Driscoll M Hanson A C Gossard
By suitable design it is possible to achieve quasi-ballistic transport in semiconductor nanostructures over times up to the ps-range. Monte-Carlo simulations reveal that under these conditions phase-coherent real-space oscillations of an electron ensemble, generated by fs-pulses become possible in wide potential wells. Using a two-color pump-and-probe technique we have been able to observe this new phenomenon in excellent agreement with the theoretical predictions. Apart from its fundamental significance, ballistic transport in nanostructures can also be used for high-efficiency coherent THz-sources. The concept of these THz-emitters and its experimental confirmation will also be presented.
Volume 67 Issue 5 November 2006 pp 849-860
Working group report: Flavor physics and model building
M K Parida Nita Sinha B Adhikary B Allanach A Alok K S Babu B Brahmachari D Choudhury E J Chun P K Das A Ghosal D Hitlin W S Hou S Kumar H N Li E Ma S K Majee G Majumdar B Mishra G Mohanty S Nandi H Pas M K Parida S D Rindani J P Saha N Sahu Y Sakai S Sen C Sharma C D Sharma S Shalgar N N Singh S Uma Sankar N Sinha R Sinha F Simonetto R Srikanth R Vaidya
This is the report of flavor physics and model building working group at WHEPP-9. While activites in flavor physics have been mainly focused on
Volume 67 Issue 5 November 2006 pp 961-981
Working group report: Heavy-ion physics and quark-gluon plasma
Munshi G Mustafa Sudhir Raniwala T Awes B Rai RS Bhalerao JG Contreras RV Gavai SK Ghosh P Jaikumar GC Mishra AP Mishra H Mishra B Mohanty J Nayak J-Y Ollitrault SC Phatak L Ramello R Ray PK Sahu AM Srivastava DK Srivastava VK Tiwari
This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported.
Volume 67 Issue 6 December 2006 pp 1119-1128 Research Articles
Pulsed pump: Thermal effects in solid state lasers under super-Gaussian pulses
Solid state laser (SSL) powers can be realistically scaled when pumped by a real, efficient and multimode pulse. In this work, a fourth-order super-Gaussian pulse was assumed as a pump for SSL’s and a complete analytical expression for the thermal phase shift is given. Moreover, the focal length of thermal lens in paraxial ray approximation regime was studied. The results when applied to a Ti: sapphire crystal show an appreciable correction for abberation compared to a top-hat pulse.
Volume 86 Issue 5 May 2016 pp 985-996 Regular
PANAHI H GAVABAR M MOHAMMADKAZEMI
The quasiexactly solvable potential method is used to determine the energies and the corresponding exact eigenfunctions for a system of N particles with equal mass interacting via an anharmonic potential. For systems with five and seven particles, we compute the ground state and the first excited state only, and compare the spectrums with the results obtained by Ritz approximation method.
Volume 86 Issue 5 May 2016 pp 1055-1066 Regular
ERMAMATOV M J YÉPEZ-MARTÍNEZ H SRIVASTAVA P C
The band structure of the proton-odd nuclei $^{153,155}$Eu, built on Nilsson orbitals, is investigated within the framework of a recently developed extended Bohr Hamiltonian model. The relative distance between spherical orbitals is taken into account by considering single-particle energies as a parameter which changes with increasing neutron number. Energy levels of each band and$B(E2)$ values inside the ground-state band are calculated and compared with the available experimental data. Thus, more comprehensive information on the structure of deformed nuclei can be obtained by studying the rotation–vibration spectra of odd nuclei built on Nilsson single-particle orbitals.
Volume 86 Issue 6 June 2016 pp 1369-1381 Regular
MISHRA S K MITTAL R KRISHNA P S R SASTRY P U CHAPLOT S L BABU P D MATSUISHI S HOSONO H
The thermal expansibilities and phase stabilities of AFe$_2$As$_2$ (A = Ca, Sr and Eu) have been investigated by powder diffraction techniques in the temperature range 5–600 K.We found the anisotropic thermal expansivities with temperature for all the compounds. The lattice parameter in the tetragonal phase (AT) of CaFe$_2$As$_2$ contracts with increasing temperature, whereas CT expands. The rate of contraction in AT is lower than the rate of expansion in CT. Other compounds show normal thermal expansion behaviour along both a- and c-axes. In-plane expansion (i.e., along the a-axis) is found to be the smallest for EuFe$_2$As$_2$ and the highest for BaFe$_2$As$_2$. However, therate of change of thermal expansivities along out-of-plane (i.e., along the c-axis) is higher as we go from Ba, Sr, Eu and Ca, respectively. Above 600 K, we notice the appearance/disappearance of certain reflections which suggest that tetragonal phase is not stable above this temperature for these compounds.
Volume 87 Issue 2 August 2016 Article ID 0030 Research Article
R NASIRAEI M R FADAVIESLAM H AZIMI-JUYBARI
This report investigated the structural, optical and electrical properties of V-doped $SnO_{2}$ thin films deposited using spray pyrolysis technique. The $SnO_{2}$:$V$ films, with different $V$-content, were deposited on glasssubstrates at a substrate temperature of $550\deg C$ using an aqueous ethanol solution consisting of tin and vanadium chloride. X-ray diffraction studies showed that the $SnO_{2}$:$V$ films were polycrystalline only with tin oxide phasesand the preferred orientations are along (1 1 0), (1 0 1), (2 1 1) and (3 0 1) planes. Using Scherrer formula, the grain sizes were estimated to be within the range of 25--36 nm. The variation in sheet resistance and optical direct band gap are functions of vanadium doping concentration. Field emission scanning electron microscopy (FESEM) revealed the surface morphology to be very smooth, yet grainy in nature. Optical transmittance spectra of the films showed high transparency of about $\approx 69--90%$ in the visible region, decreasing with increase in $V$-doping. The direct band gap for undoped $SnO_{2}$ films was found to be 3.53 eV, while for higher V-doped films it shifted toward lower energies in the range of 3.27--3.53 eV and then increased again to 3.5 eV. The Hall effect and Seebeck studies revealed that the films exhibit n-type conductivity. The thermal activation energy, Seebeck coefficient and maximum of photosensitivity in the films were found to be in the range of 0.02--0.82 eV (in thelow-temperature range), $0.15--0.18 {\rm mV K^{−1}}$ (at $T = 350 K$) and 0.96--2.84, respectively.
Volume 88 Issue 1 January 2017 Article ID 0013 Regular
Analysis of the $B^{+}_{c} \rightarrow D^{+}_{s} \bar{K}^{0\ast}$ decay
We analysed the process of $B^{+}_{c} \rightarrow D^{+}_{s} \bar{K}^{0\ast}$ using QCD factorization (QCDF) and final-state interaction (FSI) effects. First, the $B^{+}_{c} \rightarrow D^{+}_{s} \bar{K}^{0\ast}$ decay is calculated using QCDF method. The value found by using theQCDF method is less than the experimental value. Then we considered FSI effect as a sizable correction wherethe intermediate state $D^{+}^{\ast}$ mesons via the exchange of $K^{0}(K^{0}^{\ast}$) are produced. To consider the amplitudes ofthis intermediate state, the QCDF approach was used. The experimental branching ratio of $B^{+}_{c} \rightarrow D^{+}_{s} \bar{K}^{0\ast}$ decayis less than $0.4 \times 10^{-6}$ and our results are $(0.21 \pm 0.04) \times 10^{7}$ and $(0.37 \pm 0.05) \times 10^{6}$ from QCDF and FSI,respectively.
Volume 88 Issue 2 February 2017 Article ID 0036 Regular
M H MOGHTADER DINDARLU H TEHRANI M KAVOS H SAGHAFIFAR A MALEKI GH SOLOOKINEJAD M JABBARI
In this paper, an analytical model for temperature distribution of the side-pumped laser rod is extracted. This model can be used for side-pumped laser rods whose absorbed pump profile is a Gaussian profile. Then, it is validated by numerical results which exhibit a good agreement with the analytical results. Afterwards, by considering a general expression for super-Gaussian and top-hat profiles, and solving the heat equation, the influence of profile width and super-Gaussian exponent of the profile on temperature distribution are investigated.Consequently, the profile width turns out to have a greater influence on the temperature compared to the type of the profile.
Volume 88 Issue 3 March 2017 Article ID 0050 Research Article
We have investigated the influence of electron–phonon (e–p) interaction and hydrogenic donor impurity simultaneously on energy difference, binding energy, the linear, nonlinear and total refractive index changes and absorption coefficients of a hexagonal-shaped quantum wire. For this goal, we have used finite-elementmethod (FEM), a compact density matrix approach and an iterative procedure. It is deduced that energy difference and binding energy decrease by changing the impurity position with and without e–p interaction. The dipole matrix elements have complex behaviours in the presence of impurity with and without e–p interaction. The refractive index changes and absorption coefficients increase and shift towards lower energies by enhancing $a_1$ with central impurity. In the presence of central impurity, the absorption coefficients and refractive index changes enhance and shift toward higher energies when e–p interaction is considered.
Volume 89 Issue 6 December 2017 Article ID 0089 Research Article
S CHEDDADI K BOUBENDIRA H MERADJI S GHEMID F EL HAJ HASSAN S LAKEL R KHENATA
First-principle calculations on the structural, electronic, optical, elastic and thermal properties of the chalcopyrite $\rm{MgXAs_{2} (X = Si, Ge)}$ have been performed within the density functional theory (DFT) using the full potential linearized augmented plane wave (FP-LAPW) method. The obtained equilibrium structural parameters are in good agreement with the available experimental data and theoretical results. The calculated band structures reveal a direct energy band gap for the interested compounds. The predicted band gaps using the modified Becke–Johnson(mBJ) exchange approximation are in fairly good agreement with the experimental data. The optical constants such as the dielectric function, refractive index, and the extinction coefficient are calculated and analysed. The independent elastic parameters namely, $C_{11}, C_{12}, C_{13}, C_{33}, C_{44}$ and $C_{66}$ are evaluated. The effects of temperature and pressure on some macroscopic properties of $\rm{MgSiAs_{2}}$ and $\rm{MgGeAs_{2}}$ are predicted using the quasiharmonic Debye model in which the lattice vibrations are taken into account.
Volume 90 Issue 3 March 2018 Article ID 0030 Research Article
Neutron energy measurement for practical applications
M V ROSHAN H SADEGHI M GHASABIAN A MAZANDARANI
Industrial demand for neutrons constrains careful energy measurements. Elastic scattering of monoenergetic $\alpha$-particles from neutron collision enables neutron energy measurement by calculating the amount of deviation from the position where collision takes place. The neutron numbers with specific energy is obtained by counting the number of $\alpha$-particles in the corresponding location on the charged particle detector. Monte Carlo simulation and COMSOL Multiphysics5.2 are used to account for one-to-one collision of neutrons with $\alpha$-particles.
Volume 91 Issue 6 December 2018 Article ID 0088 Research Article
Nonlinear propagation of ion plasma waves in dust-ion plasma including quantum-relativistic effect
In this paper we have theoretically investigated the quantum and relativistic effects on ion plasma wave in an unmagnetised dust-ion plasma. By using the method of normal mode analysis, we have obtained a linear dispersion relation. It has been analysed numerically for quantum and relativistic effects on the propagation of ion plasma wave. By using the standard reductive perturbation technique, we have derived a Korteweg–de Vries (KdV) equation which describes the nonlinear propagation of the wave. Numerically, it is shown that only compressive type of soliton can exist in the plasma under consideration. It is found that the solitary wave profile depends significantly on the quantum and relativistic parameters. The dust size, dust charge and the dust number density are also shown to have significant influences on these solitary waves. The results of this present investigation have some relevance to the nonlinear propagation of ion plasma wave in some astrophysical, space and laboratory plasma environments.
Volume 92 Issue 4 April 2019 Article ID 0053 Research Article
Minimal length Schrödinger equation via factorisation approach
S A KHORRAM-HOSSEINI S ZARRINKAMAR H PANAHI
The fourth-order modified Schrödinger equation due to the generalised uncertainty principle is considered in one dimension with a box problem. The factorisation of fourth-order self-adjoint differential equations is then discussed and thereby the wave functions and energy spectra of themodified Schrödinger equation are derived.
Volume 93 Issue 1 July 2019 Article ID 0016 Research Article
The Weyl equation under an external electromagnetic field in the cosmic string space–time
M HOSSEINI H HASSANABADI S HASSANABADI
In this paper we have considered a massless spinor Dirac particle in the presence of an external electromagnetic field in the cosmic string space–time. To study the Weyl equation in the cosmic string framework using the general definition of Laplacian in the curved space, elements of covariant derivative have been constructed and the Weyl equation has been rewritten in the considered framework. Then we have obtained the equation ofenergy eigenvalues by using the Nikiforov–Uvarov (NU) method. The wave function has been obtained in terms of Laguerre polynomials. An important result obtained is that the degeneracy of the Minkowski space spectral is broken in the transition from Minkowski to cosmic string space.
Volume 93 Issue 2 August 2019 Article ID 0018 Research Article
F SOLTANI H BAAZIZ Z CHARIFI F EL HAJ HASSAN B HAMAD
The structural, electronic, magnetic, thermal and elastic properties of $\rm{Zn_{1−x}TM_{x}Se (TM=Mn, Co \, and \, Fe)}$ ternary alloys are investigated at $x$ = 0, 0.25, 0.50, 0.75 and 1.00 in the zincblende (B3) phase. The calculations are performed using all-electron full-potential linearised augmented plane-wave (FP-LAPW) method within the framework of the density functional theory (DFT) and the generalised gradient approximation (GGA). The electronic and magnetic properties were performed using the modified Becke–Johnson potential combined with the GGA correlation (mBJ-GGA). The electronic structures are found to exhibit a semiconducting behaviour for $\rm{Zn_{1−x}Mn_{x}Se}$ and $\rm{Zn_{1−x}Co_{x}Se}$ and a half-metallic behaviour for $\rm{Zn_{1−x}Fe_{x}Se}$ alloys at all concentrations, while CoSe with $x = 1.00$ is found to exhibit a metallic behaviour. The calculated magnetic moment per substituted transition metal (TM) Mn, Co and Fe atoms for half-metallic compounds are found to be 2.5, 1.5 and 2 $\mu_{B}$, respectively. The p–d hybridisation between the TM d- and Se p-states reduces the local magnetic moment of Mn, Co and Fe and induces small local magnetic moments on Zn and Se sites. In addition, we discuss the mechanical behaviour of binary and ternary compounds and all compounds studied here are mechanically stable.
Volume 93 Issue 5 November 2019 Article ID 0068 Research Article
$q$-Deformed oscillator algebra in fermionic and bosonic limits
S SARGOLZAEIPOR H HASSANABADI W S CHUNG A N IKOT
In this paper, the structure function corresponding to the $q$-deformed harmonic oscillator algebra is considered, where we construct the Hamiltonian by using creation and annihilation operators. Finally, the problem is investigated by evaluating the partition function of the system in finite- and infinite-dimensional Fock space for both fermionic and bosonic limits. Other thermodynamic properties such as the internal energy and the specific heat of the system are also calculated.
Current Issue
Volume 93 | Issue 5
November 2019
Click here for Editorial Note on CAP Mode
© 2017-2019 Indian Academy of Sciences, Bengaluru.