Ab initioMCDHF calculations of electron–nucleus interactions

Abstract

1 AbstractWe present recent advances in the development of atomic ab initio multiconfiguration Dirac-HartreeFock (MCDHF) theory, implemented in the GRASP relativistic atomic structure code. For neutral atoms, the deviations of properties calculated within the Dirac-Hartree-Fock method (based on independent particle model of an atomic cloud) are usually dominated by electron correlation effects, i. e. the non-central interactions of individual electrons. We present the recent advances in accurate calculations of electron correlation effects in small, medium, and heavy neutral atoms. We describe methods of systematic development of multiconfiguration expansions leading to systematic, controlled improvement of the accuracy of the ab initio calculations. These methods originate from the concept of the Complete Active Space model within the Dirac-Hartree-Fock theory, which, at least in principle, permits fully relativistic calculations with full account of electron correlation effects. The calculations within the Complete Active Space model on currently available computer systems are feasible only for very light systems. For heavier atoms or ions with more than a few electrons, restrictions have to be imposed on the multiconfiguration expansions. We present methods and tools, which are designed to extend the numerical calculations in a controlled manner, where multiconfiguration expansions account for all leading electron correlation effects. We show examples of applications of the GRASP code to calculations of hyperfine structure constants, but the code may be used for calculations of arbitrary bound-state atomic properties. In recent years it has been applied to calculations of atomic and ionic spectra (transition energies and rates), to determinations of nuclear electromagnetic moments, as well as to calculations related to interactions of bound electrons with nuclear electromagnetic moments leading to violations of discrete symmetries.

Charge radii and electromagnetic moments of At195–211

“…The full description of numerical methods, virtual orbital sets, electron substitutions, and other details of the computations can be found in Refs. [52][53][54][55].…”

Quadrupole moments of Cd and Zn nuclei: When solid-state, molecular, atomic, and nuclear theory meet

“…For almost 50 years these have been used as reference to find Q for these elements. For the recent laser experiments of Cd isotopes in an ionic state [46] V zz has been recalculated with the multi-configuration Dirac-Hartree-Fock [47] approach and found to be about 14% higher than the old result would suggest. More recent experimental and theoretical work for the 3 P 2 state of the Cd isotopes [48] has completely confirmed this finding.…”

Inverse odd-even staggering in nuclear charge radii and possible octupole collectivity in At217,218,219 revealed by in-source laser spectroscopy

“…The full description of numerical methods can be found in Ref. [29]. With the measured ratio of the b constants for the atomic ground state and the excited state at 46234 cm −1 [19], one obtains: b(46234 cm −1 )/Q S = 600(300) MHz/b.…”