Calculated rotational and vibrational g factors of LiH X ¹Σ⁺ and evaluation of parameters in radial functions from rotational and vibration‐rotational spectra

Abstract

ABSTRACT:The vibrational g factor, that is, the nonadiabatic correction to the vibrational reduced mass, of LiH has been calculated for internuclear distances over a wide range. Based on multiconfigurational wave functions with a large complete active space and an extended set of gaussian type basis functions, these calculations yielded also the rotational g factor, the electric dipolar moment, and its gradient with internuclear distance for LiH in its electronic ground state X 1 R þ . The vibrational g factor g v exhibits a pronounced minimum near internuclear distance R ¼ 3.65 Â 10 À10 m; the derivative of electric dipolar moment and the nonadiabatic matrix element coupling the electronic ground state to the first electronically excited state exhibit extrema near the same location that is also near the avoided crossing of the curves for potential energy for the electronic ground state and excited state A 1 R þ . The irreducible contribution g irr r (R) to the rotational g factor increases monotonically over the calculated domain, whereas the irreducible contribution g irr v (R) to the vibrational g factor has a minimum at the same location as that of g v itself. From these calculated radial functions, we derived values of the rotational g factor and electric dipolar moment for LiH in vibrational states v ¼ 0 and 1, and the corresponding rotational dependences, in satisfactory agreement with experimental values. These calculated data of rotational g factor served as constraints in new fits of 1000 vibration-rotational spectral data of LiH in four isotopic variants, which yield estimates of adiabatic corrections for comparison with published data and of the vibrational g factor for comparison with our calculated results.

Connecting a new non-adiabatic vibrational mass to the bonding mechanism of LiH: A quantum superposition of ionic and covalent states

“…The Sauer mass was simulated here from the vibrational g-factor data in Ref. [24]. Moving the g-factor in front of the kinetic energy operator to transform Eq.…”

Concepts in Computational Spectrometry: The Quantum and Chemistry

“…We have applied this approach to a few molecular species -H 2 [26], HeH þ [27], LiH [28], and NaCl [29] -of diverse types, but in each case not involving atomic centers of large atomic number Z because further complications would then arise from the finite and isotopically varying nuclear volume; for small Z, such effects on the spectra from finite nuclear volume are much smaller than those that might be considered to arise from finite nuclear mass [20]. This approach has been tested on comparison of radial functions for potential energy, vibrational g factor, and adiabatic corrections defined for a small domain of internuclear distance from spectral analysis with the corresponding functions from separate quantum-chemical calculations, which are not limited to a small domain.…”

Core-valence stockholder AIM analysis and its connection to nonadiabatic effects in small molecules

“…Observed minus calculated vibrational energies LiH with different recipes for the effective nuclear masses, a,39 b,40 and c. Core electron fractions and reduced masses µ (in the insets) in atomic units versus the interatomic distance R = z. (a) H + 2 , (b) H 2 , (c) HeH + , (d) LiH.…”