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 X(1)Σ(+) (υ′′ = 0–23) and a(3)Σ(+) (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(−) (X(1)Σ(+)) are all in agreement with the available experimental data. The d(3)Σ(+), 2(5)Σ(+), 1(5)Δ, and 1(5)Σ(−) quasi-bound states caused by avoided crossings were found. Calculations of the transition dipole moment of a(3)Σ(+)(1) to X(1)Σ(+)(0+) are shown. Franck-Condon factors, Einstein coefficients, and radiative lifetimes of the transition from the a(3)Σ(+)(1) (υ′ = 0–2) to the X(1)Σ(+)(0+) state are evaluated.