Volume 63, Issue 5
November 2004, pages 921-1097
pp 921-936 November 2004
Connecting Jacobi elliptic functions with different modulus parameters
The simplest formulas connecting Jacobi elliptic functions with different modulus parameters were first obtained over two hundred years ago by John Landen. His approach was to change integration variables in elliptic integrals. We show that Landen’s formulas and their subsequent generalizations can also be obtained from a different approach, using which we also obtain several new Landen transformations. Our new method is based on recently obtained periodic solutions of physically interesting non-linear differential equations and remarkable new cyclic identities involving Jacobi elliptic functions.
pp 937-945 November 2004
G P Singh R V Deshpande T Singh
We have studied five-dimensional homogeneous cosmological models with variableG and bulk viscosity in Lyra geometry. Exact solutions for the field equations have been obtained and physical properties of the models are discussed. It has been observed that the results of new models are well within the observational limit.
pp 947-961 November 2004
A Kücükbursa D I Salamov T Babacan H A Aygör
Within the quasi-particle random phase approximation (QRPA), the method of the self-consistent determination of the isovector effective interaction which restores a broken isotopic symmetry for the nuclear part of the Hamiltonian is given. The effect of the pairing correlations between nucleons on the following quantities were investigated for theA = 208 nuclei: energies of the isobar analog 0^{+} states, the isospin admixtures in the ground state of the even-even nuclei, and the differential cross-section for the^{208}Pb(^{3}He,t)^{208}Bi reaction atE(^{3}He)=450 MeV. Both couplings of the excitation branches withT^{z} = T^{0} ± 1, and the analog state with isovector monopole resonance (IVMR) in the quasi-particle representation were taken into account in our calculations. As a result of these calculations, it was seen that the pairing correlations between nucleons have no considerable effect on theT = 23 isospin admixture in the ground state of the^{208}Pb nucleus, and they cause partially an increase in the isospin impurity of the isobar analog resonance (IAR). It was also established that these correlations have changed the isospin structure of the IAR states, and shifted the energies of the IVMR states to the higher values.
pp 963-968 November 2004
Strong pionic intermittency in ‘cold’ events in^{12}C-AgBr interactions at 4.5 A GeV
Dipak Ghosh Argha Deb Asok Kumar Mallick Sharmil Asarkar Krishnadas Purkait Ranjan Sengupta
In this paper intermittent behaviour of the pions from ‘cold’ and ‘hot’ classes of events from^{12}C-AgBr interactions at 4.5 A GeV has been studied, separately. The results reveal strong intermittent pattern in case of ‘cold’ class of events.
pp 969-975 November 2004
Chemical effect on the K shell fluorescence yield of Fe, Mn, Co, Cr and Cu compounds
Chemical effects on the K shell fluorescence yields of Fe, Mn, Co, Cr and Cu compounds were investigated. Samples were excited using 59.5 keV energy photons from a^{241} Am radioisotope source. K X-rays emitted by samples were counted by a Si(Li) detector with a resolution 160 eV at 5.9 keV. Chemical effects on the K shell fluorescence yields (ωk) for Fe, Mn, Co, Cr and Cu compounds were observed. The values are compared with theoretical, semiempirical fit and experimental ones for the pure elements.
pp 977-991 November 2004
Electron impact excitation of theD states of Mg, Ca and Sr atoms: Complete experiment results
Sachin Saxena Kshamata Muktavat Rajesh Srivastava
We have used non-relativistic and relativistic distorted wave approximation methods to study the excitation of then^{1}D states of magnesium (n = 3), calcium (n = 4) and strontium (n = 5) from the ground n^{1}S state. Calculations have been performed for the complete set of parameters (σ,$$\tilde L_ \bot ^ + ,\tilde L_ \bot ^ - ,\tilde \gamma ^ + ,\tilde \gamma ^ - $$). The results are presented for electron impact energies of 20 and 40 eV. We compare our results obtained from both the non-relativistic and relativistic methods with each other. Good agreement is found on comparison and the importance of relativistic effects is also explored.
pp 993-1001 November 2004
A K Aggarwal Sushil K Kaura D P Chhachhia A K Sharma
The paper describes a simple and cost effective method for the realization of an optical interferometer based on holographic optics, which use minimal bulk optical components. The optical arrangement in the proposed method involves a very simple alignment procedure and inexpensive holographic recording material is used in the formation of holographic optical elements. The proposed interferometer set-up is quite suitable for performing optical test studies on phase (transparent) objects in real-time. Recording schemes for the formation of holographic optical elements and the related technique for the realization of the interferometer set-up along with the experimental results have been presented.
pp 1003-1010 November 2004
P K Datta Chandrajit Basu S Mukhopadhyay S K Das G K Samanta Antonio Agnesi
A non-linear mirror consisting of a lithium triborate crystal and a dichroic output coupler are used to mode-lock (passively) an Nd : YVO_{4} laser, pumped by a diode laser array. The laser can operate both in cw mode-locked and simultaneously Q-switched and mode-locked (QML) regime. The peak power of the laser while operating in QML regime is much higher but pulses suffers from poor amplitude stability. The incorporation of an acousto-optic modulator as an active Q-switch enhances the stability of the QML pulse envelope. The second-order non-linearity of powdered crystalline urea is conclusively measured with respect to KDP while the laser is operating in passively Q-switched and passively mode-locked regime as well as in actively Q-switched and passively mode-locked regime.
pp 1011-1019 November 2004
Low-frequency electrostatic dust-modes in a non-uniform magnetized dusty plasma
S S Duha S K Paul A K Banerjee A A Mamun
A self-consistent and general description of obliquely propagating low-frequency electrostatic dust-modes in a non-uniform magnetized dusty plasma system has been presented. A number of different situations, which correspond to different low-frequency electrostatic dust-modes, namely, dust-acoustic mode, dust-drift mode, dust-cyclotron mode, dust-lower-hybrid mode, and other associated modes (such as, accelerated and retarded dust-acoustic modes, accelerated and retarded dust-lower-hybrid modes, etc.), have also been investigated. It has been shown that the effects of obliqueness and inhomogeneities in plasma particle number densities introduce new electrostatic dust modes as well as significantly modify the dispersion properties of the other low-frequency electrostatic dust associated modes. The implications of these results to some space and astrophysical dusty plasma systems, especially to planetary ring-systems and cometary tails, are briefly mentioned.
pp 1021-1030 November 2004
Propagation of dust-acoustic waves in weakly ionized plasmas with dust-charge fluctuation
For an unmagnetized partially ionized dusty plasma containing electrons, singly charged positive ions, micron-sized massive negatively charged dust grains and a fraction of neutral atoms, dispersion relations for both the dust-ion-acoustic and the dustacoustic waves have been derived, incorporating dust charge fluctuation. The dispersion relations, under various conditions, have been exhaustively analysed. The explicit expressions for the growth rates have also been derived.
pp 1031-1037 November 2004
A Moorti M Raghuramaiah P A Naik P D Gupta
Temporal, spatial and spectral characteristics of a multi-keV monochromatic point x-ray source based on vacuum diode with laser-produced plasma as cathode are presented. Electrons from a laser-produced aluminium plasma were accelerated towards a conical point tip titanium anode to generate K-shell x-ray radiation. Approximately 10_{10} photons/pulse were generated in x-ray pulses of ∼18 to ∼28 ns duration from a source of ∼300 μm diameter, athυ = 4.51 keV (K_{α} emission of titanium), with a brightness of ∼10^{20} photons/cm^{2}/s/sr. This was sufficient to record single-shot x-ray radiographs of physical objects on a DEF-5 x-ray film kept at a distance of up to ∼10 cm.
pp 1039-1045 November 2004
Susanto Chakraborty Pranab Krishna Chanda
Some previously obtained physical solutions [1–3] of Yang’s equations forSU(2) gauge fields [4], Charap’s equations for pion dynamics [5,6] and their combination as proposed by Chakraborty and Chanda [1] have been presented. They represent different physical characteristics, e.g. spreading wave with solitary profile which tends to zero as time tends to infinity, spreading wave packets, solitary wave with oscillatory profile, localised wave with solitary profile which becomes plane wave periodically, and, wave packets which are oscillatory in nature.
pp 1047-1052 November 2004
Spectroscopic factors for two-proton radioactive nuclei
Spectroscopic factors for two-proton emitting nuclei are discussed in the framework of the BCS (Bardeen-Cooper-Schriefer) model. Calculations carried out for the two-proton unstable^{45}Fe,^{48}Ni and^{54}Zn nuclei are presented.
pp 1053-1062 November 2004
Scaling of cross-sections for asymmetric (e, 3e) process on helium-like ions by fast electrons
An approximate simple scaling law is obtained for asymmetric (e, 3e) process on helium-like ions for double ionization by fast electrons. It is based on the equation (Z^{′3}π) exp[-Z(r_{1} + r_{2})],Z′ = Z – (5/16) for ground state wave function of helium-like ions and Z^{′2} scaling of energies. The scaling law is found to work very well if the lower energy electron is ejected along the momentum transfer direction and the other one is ejected in the opposite direction. It also works quite well if this electron is ejected within about 90° of the momentum transfer direction with the other electron going in the opposite direction. The scaling law becomes increasingly accurate as the target nuclear charge and the energy increase.
pp 1063-1072 November 2004
Studies on ionization and excitation processes in Ps-Li scattering
Three different types of ionization and excitation processes are studied in detail for the scattering of positronium (Ps) by the simplest alkali atom (Li) using a Coulomb-Born approximation for ionization and first-Born approximation for excitation. This is the first work where orthogonalized Coulomb wave is used to represent the ionized electron for Ps-Li scattering using a single-electron and a three-electron prescription of the target. Li is chosen to minimize the effect of intrinsic correlation among the target atomic electrons so that it can extract the basic physics more accurately. All the possible Coulomb interactions are considered exactly. Comparative studies of different cross-sections using two different representations of the target provide us the informations to enrich our ideas about the system and the important role of core electrons.
pp 1073-1082 November 2004
Resonance Raman study on distorted symmetry of porphyrin in nickel octaethyl porphyrin
S Tewari R Das A Chakraborty Ramendu Bhattacharjee
The resonance Raman (RR) spectra of nickel octaethyl porphyrin, Ni(OEP), in CH_{2}Cl_{2} (solvent) at different excitations such as 514.5, 488.0, 441.6 and 406.7 nm are recorded and analysed. The results of the theory of distortion-induced RR intensity is applied to the observed spectra to determine the excited electronic state symmetry of porphyrin in Ni(OEP). It is concluded that the porphyrin molecule (D_{4h} structure) attains a non-polar distorted structure of D_{2} symmetry rather than S_{4} symmetry in CH_{2}Cl_{2} solution.
pp 1083-1087 November 2004
Relaxation between electrons and surface phonons of a homogeneously photoexcited metal film
The energy relaxation between the hot degenerate electrons of a homogeneously photoexcited metal film and the surface phonons (phonon wave vectors in two dimensions) is considered under Debye approximation. The state of electrons and phonons is described by equilibrium Fermi and Bose functions with different temperatures. Two cases for electron scattering by the metal surface, namely specular and diffuse scattering, are considered.
pp 1089-1097 November 2004
Electron lucky-drift impact ionization coefficients of ZnS : Mn
Fit of the experimental data of ZnS : Mn by a modified lucky-drift formula has been performed using the least square algorithm. The fit agrees well with the experimental data only at high field. The best fitting parameters at high field are the mean free path of order 102.74 Å and Keldysh factor,p_{0} = 0.0138. A generalized Keldysh formula has been used, due to introduction of a soft threshold factor. The soft lucky-drift theory can also be used to calculate the impact ionization coefficients of high electron energy of ZnS : Mn without losing its physical significance compared to full band-structure Monte Carlo calculation with a remarkably reduced amount of computer resources.
The curvature on semi-log plot of experimental impact ionization coefficient against the inverse of electric field is different from what is observed for other materials at low electric fields due to impact ionization of deep level impurities.
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