THEORETICAL PREDICTION OF THE SPECTROSCOPIC CONSTANTS OF FeS: AN AB INITIO MOLECULAR ORBITAL STUDY

Abstract

Author Institution: Department of Chemistry Faculty of Science, Ochanomizu University; Department of Chemistry Faculty of Science, National Institute for Advanced Interdisciplinary ResearchEnergy levels of nearly degenerated $^{5} \Delta$ and $^{5}\Sigma$ states have been studied by the MR-SDCI + Q/Roos-ANO (or various combinations of other basis sets) method with Breit-Pauli Hamiltonian for relativistic effects and spin-orbit coupling interaction corrections. The $^{5}\Sigma$ state has been predicted to be situated between $^{5}\Delta_{2}$ and $^{5}\Delta_{1}$ substates, and hence the ground state is $^{5}\Delta_{i}$. Spectroscopic constants for $^{5}\Delta$ state (and those for $^{5}\Sigma$ state) are predicted as follows: $r_{e}=2.2047$ (1.9963) \AA; $B_{0}=6043.2 (6217.1)$ MHz; $D_{0}=3.80 (3.64)$ kHz; $\nu=510.4 (543.9) cm^{-1}$; $\mu_{e}=5.92 (4.88)D$