TY - JOUR

T1 - Oscillator strengths and interstate transition energies involving 2S and 2P states of the Li atom

AU - Nasiri, Saeed

AU - Liu, Jian

AU - Bubin, Sergiy

AU - Stanke, Monika

AU - Kȩdziorski, Andrzej

AU - Adamowicz, Ludwik

N1 - Funding Information:
This work has been supported by Nazarbayev University, Kazakhstan (faculty development grant No. 021220FD3651) , and the National Science Foundation, USA (grant No. 1856702 ). L.A. also acknowledges the support of the Centre for Advanced Study (CAS) , the Norwegian Academy of Science and Letters, in Oslo, Norway, which funds and hosts the research project titled: Atto-second Quantum Dynamics Beyond the Born–Oppenheimer Approximation, during the 2021/22 academic year. The authors are grateful to the University of Arizona Research Computing and NU Research Computing for providing computational resources for this work.
Funding Information:
This work has been supported by Nazarbayev University, Kazakhstan (faculty development grant No. 021220FD3651), and the National Science Foundation, USA (grant No. 1856702). L.A. also acknowledges the support of the Centre for Advanced Study (CAS), the Norwegian Academy of Science and Letters, in Oslo, Norway, which funds and hosts the research project titled: Atto-second Quantum Dynamics Beyond the Born–Oppenheimer Approximation, during the 2021/22 academic year. The authors are grateful to the University of Arizona Research Computing and NU Research Computing for providing computational resources for this work.
Publisher Copyright:
© 2022 Elsevier Inc.

PY - 2023/1

Y1 - 2023/1

N2 - We report high accuracy calculations of the ground and excited doublet S and P states of lithium atom. Overall, 24 states corresponding to dominant electronic configurations 1s2ns and 1s2np (n=2,…,13) are considered in the framework of the Ritz variational method. The nonrelativistic wave function of each of these states is generated in an independent calculation by expanding it in terms of a large number (K=11,000−17,000) of all-electron explicitly correlated Gaussian functions (ECG) whose nonlinear parameters are extensively optimized with a procedure that employs analytic energy gradient determined with respect to these parameters. The Hamiltonian used in the calculations explicitly depends on the mass of the nucleus. The leading relativistic and quantum electrodynamics (QED) corrections to the energy levels are subsequently computed using the perturbation-theory approach and the variational nonrelativistic wave functions as the zeroth-order functions. As these functions are generated in the finite-nuclear-mass (FNM) calculations, the energy corrections include the nuclear recoil effects. The obtained energy levels allow us to determine highly accurate interstate transition frequencies for both the naturally occurring stable lithium isotopes, 6Li and 7Li, and the lithium atom with an infinitely heavy nucleus, ∞Li. The nonrelativistic wave functions are used to compute the transition dipole moments and the corresponding oscillator strengths. These quantities are reported for 144 S–P transitions of each isotope. The data set generated in this work is considerably more accurate and comprehensive than the data available from the previous theoretical calculations. It can be useful in guiding future spectroscopic measurements of the lithium atom.

AB - We report high accuracy calculations of the ground and excited doublet S and P states of lithium atom. Overall, 24 states corresponding to dominant electronic configurations 1s2ns and 1s2np (n=2,…,13) are considered in the framework of the Ritz variational method. The nonrelativistic wave function of each of these states is generated in an independent calculation by expanding it in terms of a large number (K=11,000−17,000) of all-electron explicitly correlated Gaussian functions (ECG) whose nonlinear parameters are extensively optimized with a procedure that employs analytic energy gradient determined with respect to these parameters. The Hamiltonian used in the calculations explicitly depends on the mass of the nucleus. The leading relativistic and quantum electrodynamics (QED) corrections to the energy levels are subsequently computed using the perturbation-theory approach and the variational nonrelativistic wave functions as the zeroth-order functions. As these functions are generated in the finite-nuclear-mass (FNM) calculations, the energy corrections include the nuclear recoil effects. The obtained energy levels allow us to determine highly accurate interstate transition frequencies for both the naturally occurring stable lithium isotopes, 6Li and 7Li, and the lithium atom with an infinitely heavy nucleus, ∞Li. The nonrelativistic wave functions are used to compute the transition dipole moments and the corresponding oscillator strengths. These quantities are reported for 144 S–P transitions of each isotope. The data set generated in this work is considerably more accurate and comprehensive than the data available from the previous theoretical calculations. It can be useful in guiding future spectroscopic measurements of the lithium atom.

KW - All-electron explicitly correlated gaussian function

KW - Lithium atom

KW - Oscillator strength

KW - Relativistic corrections

UR - http://www.scopus.com/inward/record.url?scp=85143511699&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85143511699&partnerID=8YFLogxK

U2 - 10.1016/j.adt.2022.101559

DO - 10.1016/j.adt.2022.101559

M3 - Article

AN - SCOPUS:85143511699

SN - 0092-640X

VL - 149

JO - Atomic Data and Nuclear Data Tables

JF - Atomic Data and Nuclear Data Tables

M1 - 101559

ER -