Electron affinity of Li7 calculated with the inclusion of nuclear motion and relativistic corrections

Abstract

Explicitly correlated Gaussian functions have been used to perform very accurate variational calculations for the ground states of 7 Li and 7 Li − . The nuclear motion has been explicitly included in the calculations ͑i.e., they have been done without assuming the Born-Oppenheimer ͑BO͒ approximation͒. An approach based on the analytical energy gradient calculated with respect to the Gaussian exponential parameters was employed. This led to a noticeable improvement of the previously determined variational upper bound to the nonrelativistic energy of Li − . The Li energy obtained in the calculations matches those of the most accurate results obtained with Hylleraas functions. The finite-mass ͑non-BO͒ wave functions were used to calculate the ␣ 2 relativistic corrections ͑␣ =1/c͒. With those corrections and the ␣ 3 and ␣ 4 corrections taken from Pachucki and Komasa ͓J. Chem. Phys. 125, 204304 ͑2006͔͒, the electron affinity ͑EA͒ of 7 Li was determined. It agrees very well with the most recent experimental EA.

Lowest-order relativistic corrections of helium computed using Monte Carlo methods

“…Starting with the work of Hylleraas in the 1920s, explicitly correlated wave functions have been used to determine the nonrelativistic energies, the relativistic corrections (both lowest and higher order), the mass related corrections, and some QED corrections for helium [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and lithium [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] to an accuracy that meets or exceeds the current level of experimental precision. This excellent agreement between theory and experiment is not yet true for the other atoms.…”

Isotope shift in the electron affinity of lithium

“…9 More recently two high accuracy calculations on the 7 Li EA were reported. 10,11 In the work by Pachucki and Komasa, 10 the INM variational calculations on 7 Li and 7 Li − employing explicitly correlated Gaussians were performed first and the INM wave functions for these systems were subsequently used to calculate the finite-mass corrections, as well as the relativistic and QED corrections. In Ref.…”

Orbit-orbit relativistic corrections to the pure vibrational non-Born-Oppenheimer energies of H2

“…Our contribution to the field has been the recent calculations concerning four electron atomic systems, Be and Li − . [4][5][6] In those works we have used wave functions expanded in terms of Gaussian functions that explicitly depend on the interparticle distances ͓the so-called explicitly correlated Gaussians ͑ECG͔͒ and obtained in calculations where the Born-Oppenheimer ͑BO͒ approximation is not assumed in the perturbative evaluation of the ␣ 2 relativistic effects. With those effects added to the nonrelativistic energies and with the QED corrections calculated up to the order of ␣ 4 by Pachucki and Komasa 7-9 also included, we obtained results matching the experimental ionizations potentials and transition frequencies within the experimental accuracy.…”