Spectroscopic properties and potential energy curves for 27 electronic states of TcH

Abstract

State-averaged complete active space self-consistent field followed by first-order configuration interaction and multireference singles + doubles CI calculations are carried out on 27 low-lying electronic states of TcH. In addition spin-orbit effects on low-lying states are studied. The ground state of TcH is found to be of 7Σ + symmetry ( R e = 1.75 A ̊ , ω e = 1633 cm −1, D e = 2.6 eV) with a very low-lying excited state of 5Σ + symmetry ( T e ∼ 2619 cm −1). Ten low-lying bound states below 20 000 cm −1 are found. Many spectroscopic transitions in the far IR-UV regions are predicted for TcH which are yet to be observed. The analyses of the wavefunctions, dipole moments, and Mulliken populations reveal that all the low-lying electronic states of TcH are very ionic (Tc +H −). The TcH bonds in most of the states are composed of spd hybrid bonds of the metal atom. The TcH σ bond in the 7Σ + ground state is composed of 36% Tc( s), 23% Tc( p), and 41% Tc( d) character while in the 5Σ + state, the σ bond is made of 50% Tc( s), 3% Tc( p), and 47% Tc( d).