icMRCI+Q Study of the Spectroscopic Properties of the 14 Λ-S and 49 Ω States of the SiN- Anion in the Gas Phase.

This paper calculates the potential energy curves of the 14 Λ-S and 49 Ω states, which come from the first three dissociation channels of the SiN- anion. These calculations are conducted using the valence internally contracted multireference configuration interaction and the Davidson correction approach. Core-valence correlation and scalar relativistic corrections are taken into account. The potential energies are extrapolated to the complete basis set limit. The spin-orbit coupling is computed using the state interaction approach with the Breit-Pauli Hamiltonian. We found that the X¹Σ⁺ (υ'' = 0-23) and a³Σ⁺ (υ' = 0-2) states of SiN- are stable at the computed adiabatic electron affinity value of 23,262.27 cm-1 for SiN. Based on the calculated potential energy curves, the spectroscopic parameters and vibrational levels were determined for all stable and metastable Λ-S and Ω states. The computed adiabatic electron affinity of SiN and the spectroscopic constants of SiN- (X¹Σ⁺) are all in agreement with the available experimental data. The d³Σ⁺, 2⁵Σ⁺, 1⁵Δ, and 1⁵Σ- quasi-bound states caused by avoided crossings were found. Calculations of the transition dipole moment of a³Σ⁺₁ to X¹Σ⁺0+ are shown. Franck-Condon factors, Einstein coefficients, and radiative lifetimes of the transition from the a³Σ⁺₁ (υ' = 0-2) to the X¹Σ⁺0+ state are evaluated.