D K Rai
Articles written in Pramana – Journal of Physics
Volume 14 Issue 5 May 1980 pp 379-388 Spectroscopy
Emission spectrum of DyO molecule has been photographed under high resolution in the wavelength region 5000 to 6300 A. The observed bands have been arranged into three different band systems. The rotational structure in the (0, 0) band of system I is partially resolved and analysed. Isotopic shifts have been calculated for various isotopic molecules and compared with observations. Electronic states involved in the transitions have been discussed.
Volume 16 Issue 2 February 1981 pp 147-150 Molecular Spectroscopy
The C-X system of diatomic mercury chloride has been re-investigated in emission. The previous vibrational assignments of this system by Horne and others have been confirmed by measurement of the chlorine isotopic shift and improved vibrational constants for the ‘C’ state determined.
Volume 19 Issue 6 December 1982 pp 579-592 Experimental Techniques
We describe a new method for the polarization of an electret foil which has proved very convenient and yields a foil having very good performance in a microphone. The variations in the charge accumulation on the electret foil and its decay with time as well as the variation of the microphone sensitivity with different microphone parameters
A brief description of the photoacoustic spectrometer including microphone biasing and the photoacoustic cell is given. The photoacoustic spectra of some rare earth oxides in the form of powders have been recorded. It is seen that the atomic levels of triplyionized rare earths which are not fluorescent appear very prominently in the photoacoustic spectrum. The spectra for terbium and praseodymium oxides do not show clear peaks probably due to the presence of different stoichiometric forms.
Volume 20 Issue 2 February 1983 pp 157-162 Atomic And Molecular Physics
Total cross-section for electron impact excitation of the resonance levels in Li, Na and K are calculated using the method due to Crothers and McCarroll. The results are compared with other available theoretical and experimental data.
Volume 23 Issue 2 August 1984 pp 215-219 Atomic And Molecular Physics
The photoacoustic spectra of Rhodamine 6G (Rh6G), Rhodamine B (RhB) dyes and their mixtures were recorded at different concentrations. It is observed that in the mixture the photoacoustic signal increases due to excitation transfer from Rh6G to RhB in the wavelength region 480–530 nm. The excitation transfer rate estimated from these data show that resonance is dominant rather than the collisional transfer process.
Volume 25 Issue 2 August 1985 pp 175-177 Atomic And Molecular Physics
The effect of including distortion (with and without exchange) in the wavefunction for the continuum electron while calculating the probability of autoionization of 2
Volume 28 Issue 2 February 1987 pp 167-179 Atomic And Molecular Physics
Coulomb-projected Born methods for the theoretical study of electron impact excitation of hydrogen and helium are reviewed. The results obtained by using different forms of Coulomb-projected Born methods are compared with other theoretical and experimental results and analyzed. The inadequacy of the variable charge Coulomb-projected Born approximation (VCCPB)—the most recent form of the Coulomb-projected Born methods—in giving good results in processes where exchange is dominant is discussed in detail. The ‘modified’ VCCPB approximation obtained by modifying the VCCPB method to remove its shortcomings is also discussed and its application to electron impact excitation of 23
Volume 29 Issue 2 August 1987 pp 163-166 Atomic And Molecular Physics
Doppler limited laser optogalvanic (LOG) spectra are obtained by irradiating a bromine discharge with a cw dye laser. The discrete bands of the Br2
Volume 35 Issue 3 September 1990 pp 341-348 Research Articles
Calculation of cross-sections for the two-electron excitation in helium-like ions by electron impact employing Coulomb-Born-Oppenheimer (CBO) approximation is presented. Analytical expressions for the differential and total scattering cross-sections without using partial wave expansion of the wavefunction reported earlier have been used. The total and differential scattering cross-sections for each of the excitations 1
Volume 38 Issue 1 January 1992 pp 77-90
We have calculated total and differential cross-sections for 1
Volume 41 Issue 2 August 1993 pp 175-184 Research Articles
Proton induced X-ray emission has been used to measure
Volume 45 Issue 3 September 1995 pp 271-278
Two photon absorption spectrum of
Volume 50 Issue 5 May 1998 pp 405-418 Research Articles
Fluorescence spectrum of Dy3+, Dy3+-Ho3+, Tb3+ and Tb3+-Er3+ doped in calibo glass have been studied using Ar+ and excimer lasers. Non-radiative energy transfer from trivalent dysprosium and terbium (donors) to holmium and erbium (acceptors) respectively has been observed on the basis of decrease in the life time of the levels and reduction in fluorescence intensity of Dy3+ and Tb3+ on increasing Ho and Er concentrations. The interaction mechanism of donor and acceptor ions is found to be dipole-dipole in both cases. Various parameters such as donor-acceptor distances, non-radiative energy transfer efficiency (
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