Arijit Ghoshal

Positron scattering from hydrogen atom embedded in dense quantum plasma

Scattering of positrons from the ground state of hydrogen atoms embedded in dense quantum plasma has been investigated by applying a formulation of the three-body collision problem in the form of coupled multi-channel two-body Lippmann-Schwinger equations. The interactions among the charged particles in dense quantum plasma have been represented by exponential cosine-screened Coulomb potentials. Variationally determined hydrogenic wave function has been employed to calculate the partial-wave scattering amplitude. Plasma screening effects on various possible mode of fragmentation of the system e++H(1s) during the collision, such as 1s→1s and 2s→2s elastic collisions, 1s→2s excitation, positronium formation, elastic proton-positronium collisions, have been reported in the energy range 13.6-350 eV. Furthermore, a comparison has been made on the plasma screening effect of a dense quantum plasma with that of a weakly coupled plasma for which the plasma screening effect has been represented by the Debye model. ...

Ground states and doubly excited resonance states of H− embedded in dense quantum plasmas

We have made an investigation on the ground states and the 2s21Se resonance states of H− in dense quantum plasmas. Exponential-cosine-screened Coulomb potentials (ECSCP) are used to represent the effective potential for a test charge in dense quantum plasmas. Ground-state energies and wavefunctions are determined within the framework of Ritzs variational principle by employing highly correlated wavefunctions to take into account the correlation effect of the charged particles. Ground-state energies are shown to converge with the increase of terms in the wavefunctions. We also report various expectation values of the coordinates of electrons in H−. Resonance energies and widths for the doubly excited H− for various values of the screening parameter are determined using the stabilization method by calculating the density of the resonance states. Results for resonance energies and widths are reported for the screening parameter in the range 0.0–0.15. Such a calculation for H− is reported for the first time in the literature.

Elastic scattering of positrons from hydrogen atoms with exponential cosine-screened Coulomb potentials

We have investigated the elastic scattering of positrons from the ground state of hydrogen atoms interacting with exponential cosine-screened Coulomb potential (ECSCP). A simple expression for partial-wave scattering amplitude, derived within the framework of the second-order distorted wave Born approximation, has been used to calculate the scattering parameters. A detailed study has been made on differential and total cross sections in the energy range 20?300?eV. To the best of our knowledge, this study on the differential and total cross sections for elastic positron?hydrogen collisions in ECSCP is reported for the first time.

Dynamics of e+ + H(ns) → e+ + H(n′s) with exponential cosine-screened Coulomb potentials

The dynamics of ns???n?s excitations of hydrogen by positron impact with exponential cosine-screened Coulomb potentials (ECSCPs) has been investigated using a distorted-wave theory in momentum space. Making use of a simple variationally determined wave function for the hydrogen atom, it has been possible to obtain the distorted-wave scattering amplitude in a closed analytical form. A detailed study has been made on differential and total cross sections in the energy range 20?250?eV. To the best of our knowledge, such a study on the differential and total cross sections for inelastic positron?hydrogen collisions with ECSCPs is the first reported in the literature.

Dynamics of positronium formation in positron-hydrogen collisions embedded in weakly coupled plasmas

Dynamics of positronium (Ps) formation in an arbitrary s-state from an arbitrary s-state of the hydrogen atom in weakly coupled plasma has been investigated within the framework of a distorted-wave theory. The interactions among the charged particles in the plasma have been represented by Debye-Huckel potentials. Using simple variational hydrogenic wave functions and arbitrary order derivatives of the general three-denominator Lewis integral partial-wave scattering amplitudes have been obtained in closed forms. These distorted-wave scattering amplitudes have been used to make a detailed study on differential and total cross sections. It has been found that screening of the interaction potentials has significant effect on the scattering dynamics. Some notable features of cross sections have also been revealed.

Borromean bindings in muonic molecular ions with screened Coulomb potentials

We have investigated the stability of muonic molecular ions interacting with screened Coulomb potentials of various strengths. Particular emphasize has been given to study the Borromean bindings in these ions. Two types of screened potentials are considered, namely, static screened Coulomb potentials and exponential cosine-screened Coulomb potentials. Making use of extensive correlated variational wavefunctions, Borromean windows for these ions are determined accurately. The possibility of existence of Borromean binding for other three-body systems has also been explored. Moreover, the results for ground state energies, excited states energies and several expectation values associated with ppμ, ddμ and tdμ molecular ions are reported for various values of the screening parameter.

Positron impact excitations of hydrogen atom embedded in weakly coupled plasmas: Formation of Rydberg atoms

Formation of Rydberg atoms due to 1s→nlm excitations of hydrogen, for arbitrary n, l, m, by positron impact in weakly coupled plasma has been investigated using a distorted-wave theory in the momentum space. The interactions among the charged particles in the plasma have been represented by Debye-Huckel potentials. Making use of a simple variationally determined wave function for the hydrogen atom, it has been possible to obtain the distorted-wave scattering amplitude in a closed analytical form. A detailed study has been made on the effects of plasma screening on the differential and total cross sections in the energy range 20–300 eV of incident positron. For the unscreened case, our results agree nicely with some of the most accurate results available in the literature. To the best of our knowledge, such a study on the differential and total cross sections for 1s→nlm inelastic positron-hydrogen collisions for arbitrary n, l, m in weakly coupled plasmas is the first reported in the literature.

Positron scattering from hydrogen atom embedded in weakly coupled plasma

The positron-hydrogen collision problem in weakly coupled plasma environment has been investigated by applying a formulation of the three-body collision problem in the form of coupled multi-channel two-body Lippmann-Schwinger equations. The interactions among the charged particles in the plasma have been represented by Debye-Huckel potentials. A simple variational hydrogenic wave function has been employed to calculate the partial-wave scattering amplitude. Plasma screening effects on various possible mode of fragmentation of the system e++H(1s) during the collision, such as 1s→1s and 2s→2s elastic collisions, 1s→2s excitation, positronium formation, elastic proton-positronium collisions, have been reported. Furthermore, a detailed study has been made on differential and total cross sections of the above processes in the energy range 13.6-350 eV of the incident positron.

Scattering of slow electrons by hydrogen atoms in weakly coupled Debye plasmas

An effective range theory is used to study the elastic scattering of electrons by the ground state of hydrogen atoms in weakly coupled plasma environments for low electron energies. The plasma screening effect is represented by screened Coulomb potentials (SCPs) of Debye type. Highly correlated and variationally determined wavefunctions for H− in plasmas are used to determine the effective range of the ion states. The results for S-wave singlet phase shifts for the incident electron momentum in the range [0, 0.75] au are reported, to the best of our knowledge, for the first time in the literature. For the unscreened case, our reported results are in good agreement with some of the most accurate results available in the literature.

Positron impact excitations of hydrogen atom embedded in dense quantum plasmas: Formation of Rydberg atoms

Formation of Rydberg atoms due to 1 s → nlm excitations of hydrogen by positron impact, for arbitrary n, l, m, in dense quantum plasma has been investigated using a distorted wave theory which includes screened dipole polarization potential. The interactions among the charged particles in the plasma have been represented by exponential cosine-screened Coulomb potentials. Making use of a simple variationally determined hydrogen wave function, it has been possible to obtain the distorted wave scattering amplitude in a closed analytical form. A detailed study has been made to explore the structure of differential and total cross sections in the energy range 20–300 eV of incident positron. For the unscreened case, our results agree nicely with some of the most accurate results available in the literature. To the best of our knowledge, such a study on the differential and total cross sections for 1 s → nlm inelastic positron-hydrogen collisions in dense quantum plasma is the first reported in the literature.