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Purkait M.,Ramakrishna Mission Residential College
Journal of Physics: Conference Series | Year: 2015

Double-differential cross sections (DDCS) for electron emission in ionization under the impact of dressed projectiles has been calculated within the framework of three-Coulomb wave (3CW) model. The interaction between the dressed projectile ion and the active electron is approximated by a model potential. In order to take into account of the effect of the passive electrons, we have also constructed a model potential which satisfies initial condition and the corresponding wave function has been calculated from the model hamiltonian of the active electron in the target. © Published under licence by IOP Publishing Ltd. Source


Mondal S.,Korea Astronomy and Space Science Institute | Mondal S.,Ramakrishna Mission Residential College | Choi C.S.,Korea Astronomy and Space Science Institute
New Astronomy | Year: 2013

In the present study, we notice that within a few gravitational radii, where the X-ray emission originates, the perturbations in the accretion disk may excite high frequency quasi-periodic oscillations (QPOs). The vertical and the radial disk oscillations frequencies due to the perturbation exhibit a 3:2 twin-peak ratio which is most commonly detected in the X-ray fluxes in many Galactic micro-quasars. The high frequency QPOs happen most likely if the oscillations occur very close to the center. We further notice that the perturbations originate in the neighborhood of the shock transition or from a discontinuity in the disk, and could be the possible mechanism to excite the high frequency QPOs. The shocks are more probable in the X-ray emission region and may form very close to the horizon particularly, when the black hole spin is very high. Studying the shock locations as a function of the black hole spin in a fully general relativistic inviscid transonic accretion flows, we calculate the disk oscillation frequencies and their ratios in that perturbed orbit. Further, from the spin dependence, we estimate the 'most probable spin interval' in the micro-quasars by considering the 1/M scaling hypothesis in high frequency QPOs. Finally, we find the spin (a) interval which lies for XTE 1550-564, at a ∼ (0.89-0.99), for the GRO 1655-40, at a ∼ (0.96-0.99) and for the GRS 1915+105, at a ∼ (0.74-0.999). The uncertainty in the mass analysis corresponds to the above spin intervals. © 2012 Elsevier B.V. All rights reserved. Source


Samanta R.,Ramakrishna Mission Residential College | Purkait M.,Ramakrishna Mission Residential College
Physica Scripta | Year: 2011

Single-electron capture in p-He collisions has been calculated at incident projectile energies ranging from 20 to 11 000 keV by means of the four-body boundary corrected continuum intermediate state approximation. The effect of dynamic electron correlations is explicitly taken into account through the complete perturbation potentials. Total single-electron capture cross-sections have been calculated by summing over the contributions up to n=2 shells and sub-shells. The differential cross-sections are calculated at impact energies in the range from 30 to 300 keV. Overall, the calculated cross-sections are in good agreement with recent experimental findings. © 2011 The Royal Swedish Academy of Sciences. Source


Samanta R.,Ramakrishna Mission Residential College | Purkait M.,Ramakrishna Mission Residential College | Mandal C.R.,Jadavpur University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

Cross sections for single-electron capture in collisions of He2 +, Liq+ (q = 1,2,3), C6+, and O8+ ions with helium atoms at incident energy ranging from 50 to 5000 keV/amu have been calculated in the framework of four-body boundary-corrected continuum intermediate state (BCCIS-4B) approximation in both prior and post forms. In this formalism, distortion in the final channel related to the Coulomb continuum states of the projectile ion and the active electron in the field of residual target ion are included. In all cases, total single-electron-capture cross sections have been calculated by summing over all contributions up to n = 3 shells and subshells, respectively. It has been observed that the contribution of the capture cross section into the excited states is significant for asymmetric collision (ZP>lZT) and is insignificant for symmetric collision. Numerical results for the total cross sections show good agreement with the available experimental findings, particularly in the post form. Post-prior discrepancy has been found to be within 30% except for Li + + He interactions below 150 keV/amu. © 2011 American Physical Society. Source


Samanta R.,Ramakrishna Mission Residential College | Purkait M.,Ramakrishna Mission Residential College
European Physical Journal D | Year: 2011

Four-body formalism of boundary corrected continuum intermediate state (BCCIS-4B) approximation have been applied to calculate the single-electron capture cross sections by fast protons through some helium-like ions in a large energy range from 30-1000 keV. In this model, distortion has been taken into account in the entrance channel. In the final channel, the passive electron plays the role of screening of the target ion. However, continuum states of the projectile and the electron in the field of the residual target ion are included. The comparison of the results is made with those of other theoretical investigations and experimental findings. The present calculated results are found to be in good agreement with the available experimental findings. © 2011 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg. Source

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