Valence photodetachment of Li−and Na−using relativistic many-body techniques

Abstract

The multiconfiguration Tamm-Dancoff technique (MCTD) is applied to study photodetachment of negative ions of lithium and sodium. A cusplike structure is found in the photodetachment cross section just below the first detachment-plus-excitation threshold of Li − (Li 2p), and of Na − (Na 3p), in qualitative agreement with existing theoretical and experimental results. The current work emphasizes the importance of correlation in the form of configuration interaction in the photodetachment process and demonstrates the utility of MCTD in dealing with highly correlated systems.

Photoionization study of Xe 5s: ionization cross sections and photoelectron angular distributions

“…The various final excited and continuum are coupled together (interchannel coupling) in exactly the same manner as in RRPA [3,4]; the only difference being that here there are extra channels that arise from two-electron excitation processes, photoionization-plus-excitation. The full theoretical framework, as employed herein, has been presented earlier [9].…”

“…disagreement between theory and experiment has underscored the importance of including non-RPA correlations to obtain better agreement between theory and experiment. A possible approach to the problem is the relativistic multiconfiguration Tamm-Dancoff (MCTD) [8,9] technique that we are developing which includes a number of non-RPA correlations. Hence, the thrust of the present work is on testing the use of the MCTD technique.…”

Outer-shell photodetachment of Li− near inner-shell thresholds

“…To deal with this phenomenology more accurately, we have embarked upon a program to explore this effect in negative atomic ions, and, as a first step, we have looked at the photodetachment of the simplest closed-shell negative ion with more than one shell, Li − in the ground 1s 2 2s 2 state, using a version of the Belfast R-matrix methodology that has been modified to accommodate photodetachment [18]. Although the photodetachment of Li − has been the subject of a number of studies, both experimental and theoretical, these investigations scrutinized only the low-energy region, from threshold to about 6 eV [19][20][21][22][23][24][25][26][27][28][29][30] and the inner-shell cross sections around the opening of the K-shell [31][32][33][34]18]; there have been no studies of the outer-shell cross sections at the higher energies. Since the threshold region has been the subject of a number of investigations, the present study omits that region; our calculation spans the 10-100 eV photon energy range.…”

Photoionization of atomic barium subshells in the4dthreshold region using the relativistic multiconfiguration Tamm-Dancoff approximation

“…is the eigen value of the ground state orbital (hole) a , ω is the photon energy. The inhomogeneous term a R describes the interchannel coupling and can be written as ------(2) describes the coupling between channels, a B describes the coupling with transitions ' b b → between valence orbitals leading to excited-bound (XB) states and a L is the term with Lagrange multipliers ensuring the orthogonality to the ground state orbitals.The multichannel RMCTD excited-state wavefunction with total angular momentum J, M has the form[13,42] functions obtained from one of the initialstate configurations ("parent" configuration) by photoexciting a valence orbital (hole a) to a continuum orbital, a , or to another initial vacant state (valence) orbital, respectively. i γ and j γ represent all other quantum numbers required to define the corresponding configurations uniquely.…”