P. K. Mukherjee

Energy levels and structural properties of compressed hydrogen atom under Debye screening

Time dependent variation perturbation calculations have been performed for estimating the transition energies, os- cillator strengths and transition probability values for a few dipole allowed states of compressed hydrogen atom confined in a weakly coupled plasma. The compression is obtained by embedding the atom at the centre of an impenetrable spherical box. The dipole polarizability of the atom is evaluated at each confinement radius with respect to different plasma screening param- eters. The effect of pressure due to spatial confinement on the dipole polarizability and other atomic properties is analyzed. Results obtained are useful for the diagnostic determination of astrophysical and laboratory plasmas and for the calculation of collision rate coefficients needed for computing opacity of stellar envelopes - a quantity of importance in the context of stellar structure and pulsations.

Electron affinity of positronium embedded in Debye plasma

Abstract The effect of environment like that of a plasma on the ground state energy of positronium minus ion (Ps − ) has been estimated variationally using multi-term correlated basis sets. Debye model has been applied to include the plasma screening effect in the interaction energy between two charge particles. The electron affinity of positronium is estimated for different Debye screening parameters and is found to decrease monotonically with increasing screening.

Time-dependent perturbation calculations for transition properties of two-electron atoms under Debye plasma

Abstract Systematic investigation have been performed for the dynamic polarizabilities, energy levels, oscillator strengths and transition probabilities for the first few members of helium isoelectronic series He, Li+,Be2+,B3+ and C4+ embedded in the Debye plasma. The effect of plasma is described by introducing an exponential screening (the Debye screening) to the nuclear Coulomb potential. Systematic trend is observed for all the properties under study with respect to increased screening. The ionization potential decreases with an increased screening and the number of bound excited states supported by the Debye screened potential is finite.

Magnetic multipole transitions of a stripped carbon ion in a variety of Debye plasmas

Survival of the excited triplet states and the spin-forbidden transitions including the magnetic dipole (M1) and magnetic quadrupole (M2) decays in the two-electron ion embedded in a variety of Debye plasmas are investigated theoretically. The dependence of the transition energy on the plasmas screening strength exhibits remarkably opposite patterns for the principal quantum number conserving and the non-conserving transitions. The magnetic multipole decay rates of the lower-lying states are seen to remain less affected at lower values of the screening magnitude.

Effect of Debye plasma on the structural properties of compressed positronium atom

The effect of weakly coupled plasma on the energy levels and other structural properties of compressed positronium atom has been analysed. The positronium atom is treated as a quasistable system and the compression is obtained by embedding the atom at the centre of an impenetrable spherical box. The dipole polarizabilities, transition energies, oscillator strengths and transition probabilities of a few low lying allowed excited states have been obtained for various plasma strengths with different confinement radii.

Time-dependent Hartree-Fock calculations for the excited ‘S’ states of lithium isoelectronic sequence

Time-dependent HF (RPA) calculations have been performed to estimate the transition energies and excited state wavefunctions of Li, Be+, B2+ and C3+ for the transitions 1s22s∶ 2S → 1s2ns ∶ 2S (n = 3,4, ... 8). The excitation energies and excited state wavefunctions are extracted from the position of the poles of a linearised variational functional. The excitation energies are in excellent agreement with those obtained spectroscopically. The excited state wavefunctions are utilised to find the matrix elements of different operators and the cusp values.

Spectral line shifts of alkali atoms in liquid helium: a relativistic density functional approach

Excitation line shifts of the principal resonance transitions in alkali atoms sodium and cesium embedded inside the liquid helium environment have been calculated using four-component relativistic density functional theory. The effect of the liquid helium environment is assumed to be represented by a cluster of 14 atoms surrounding the central alkali atom. The estimated blue shift of the principal resonance line 2S →2P is 22.8 nm for Na and 16.7 nm for Cs. The result for Cs is in good agreement with the experimental shift of 18.2 nm. In the absence of the experimental data for Na, our result is compared with those of other theoretical estimates.

Variational calculation for the doubly excited state (2p2)3Pe of BeIII

Nonrelativistic energy of the (2p(2))(3)P(e) state of Be(2+) has been calculated using Ritz-variational method. The trial wave function is of Hylleraas type. The upper-bound energy E=-3.382 712 420 77 a.u. calculated by us is the lowest yet obtained.

Static dipole polarizabilities of open-shell negative ions

SummaryDipole polarizability estimates at λ ⇒ ∞ have been calculated for the 2p and 3p open-shell negative ions in their ground and valence excited states. To complete the sequence such estimates for F− and Cl− in their ground1S state have also been made. Single configuration based linear response theory has been adopted presently with a view to study the effect of RPA-type correlations on the polarizabilities of such systems. For the 3p open-shell systems the innermost 1s core has been kept frozen. Most of the results are reported for the first time. Agreement with existing data, wherever available, is reasonable. The convergence of the polarizability estimates towards basis sets has been studied.

Magnetic quadrupolar (M2) transition probabilities and triplet excited Rydberg states of helium-like ions

A detailed study of the spin forbidden transitions, 1s2 1S → 1snp 3P (n = 2,... 7) has been carried out for the first five members of the helium isoelectronic sequence. Non-relativistic time-dependent coupled Hartree-Fock (TDCHF) theory with a spin dependent perturbation has been used to this end. Transition energies for the various excited states generated, have been obtained and suitable analytic representations for these high lying Rydberg states have been given. Also, the magnetic quadrupolar (M2) transition rate has been calculated with the help of the wavefunctions so obtained. These compare favourably with existing data.