Calculations of electronic properties and vibrational parameters of alkaline-earth lithides: MgLi^+ and CaLi^+

TL;DR

This study investigates the electronic and vibrational properties of MgLi^+ and CaLi^+ molecular ions, providing new calculations of their spectroscopic constants, moments, polarizabilities, and vibrational lifetimes, including effects of higher correlation and adiabatic corrections.

Contribution

First-time calculations of quadrupole moments and static dipole polarizabilities for MgLi^+ and CaLi^+ ions, along with vibrational energies and lifetimes using advanced quantum methods.

Findings

Vibrational lifetimes of MgLi^+ and CaLi^+ are around 3 seconds at room temperature.

Highly excited vibrational states have significantly longer lifetimes than ground states.

Electronic excited states of these ions were also characterized using EOM-CCSD method.

Abstract

The ^1{\Sigma}^+ electronic ground states of MgLi^+ and CaLi^+ molecular ions are investigated for their spectroscopic constants and properties such as the dipole- and quadrupole moments, and static dipole polarizabilities. The quadrupole moments and the static dipole polarizabilities for these ions have been calculated and reported here, for the first time. The maximum possible error bars, arising due to the finite basis set and the exclusion of higher correlation effects beyond partial triples, are quoted for reliability. Further, the adiabatic effects such as diagonal Born-Oppenheimer corrections are also calculated for these molecules. The vibrational energies, the wavefunctions, and the relevant vibrational parameters are obtained by solving the vibrational Schr\"odinger equation using the potential energy curve and the permanent dipole moment curve of the molecular electronic ground state. Thereafter, spontaneous and black-body radiation induced transition rates are calculated to obtain the lifetimes of the vibrational states. The lifetime of rovibronic ground state for MgLi^+ , at room temperature, is found to be 2.81 s and for CaLi^+ it is 3.19 s. It has been observed that the lifetime of the highly excited vibrational state is several times larger than (comparable to) that of the vibrational ground state of MgLi^+ (CaLi^+ ). In addition, a few low-lying electronic excited states of {\Sigma} and {\Pi} symmetries have been investigated for their electronic and vibrational properties, using EOM-CCSD method together with the QZ basis sets.