Lowest electronic states of neutral and ionic LiN

Abstract

We have investigated the potential energy curves (PECs) of the LiN
heteronuclear diatomic molecule, including its ionic species LiN⁺ and LiN⁻,
using explicitly correlated multi-reference configuration interaction
(MRCI-F12) calculations in conjunction with the correlation consistent
quintuple-𝜁 basis set. The effect of core–valence correlation, scalar
relativistic effects, and the size of the basis sets has been
investigated. A comprehensive set of spectroscopic constants determined
based on the above-mentioned calculations are also reported for the
lowest electronic states and all systems, including dissociation
energies, harmonic and anharmonic vibrational frequencies, and
rotational constants. Additional parameters, such as the dipole moments,
equilibrium spin-orbit constants, excitation energies, and
rovibrational energy levels, are also documented. We found that the
three triplet states of LiN, namely, X ³∑⁻, A ³Π, and 2 ³∑⁻,
exhibit substantial potential wells in the PEC diagrams, while the
quintet states are repulsive in nature. The ground state of the anion
also shows a deep potential well in the vicinity of its equilibrium
geometry. In contrast, the ground and excited states of the cation are
very loosely bound. Charge transfer properties of each of these states
are also analyzed to obtain an in-depth understanding of the interatomic
interactions. We found that the core–valence correlation has a
substantial effect on the calculated spectroscopic constants.