Electronic transition dipole moment and radiative lifetime calculations of sodium dimer ion-pair states

Abstract

We report here ab initio calculated electronic transition dipole moments for the sodium dimer ion pair states of (1)Σg (+) symmetry. They vary strongly as a function of internuclear distance because of the effect of the Na(+) + Na(-) ion pair potential, which also causes the formation of additional wells and shoulders in the molecular potential energy curves. We also present a computational study of the transition dipole moment matrix elements and lifetimes for these ion-pair states.

Up and away in the potential landscape of diatomic molecule potential energy curves

“…For atoms with a positive electron affinity, the atomic ion pair asymptote lies below the asymptote of a neutral atom plus an atomic ion and free electron. The experiments of [78] showed the strong influence of the 1/R ion pair potential on a variety of potentials of various excited 1 Σ g + states of Na 2 , in accord with the theory of [79,80] and many later calculations (see also [82] and references therein). Recent work at UConn [80] has focused on Rb 2 , where the "Heavy" Rydberg asymptote, Rb + + Rb -, lies slightly below the Rb(5s 2 S) + Rb(8p 2 P 1/2 ) asymptote.…”

Time-Resolved Vibrational Spectroscopy to Measure Lifetime of the E$^3Π_g(v=3)$ state of Molecular Iodine

“…There have been small number of lifetime measurements in molecules compared to the lifetime measurements in atoms. There are still lack of excited state lifetime measurements in some important ion-molecules, alkali hydride molecules and alkali dimer ion-pair states [25,26,27,28,29]. In this study we present for the first time lifetime measurement of the vibrational level of the E 3 Π g (v=3) molecular state of I 2 by means of two-step double-resonance pulse excitation spectroscopy.…”

“…This is specifically important because the E-state correlates diabatically with the ground state I − ( 1 S o )+I + ( 3 P 2 ) of the separated ions and diabatic dissociation limit corresponds to about 72000 cm −1 [32]. Recently, calculated radiative lifetimes for the alkali dimer ion pair states have revealed strong variations as a function of internuclear distance because of the effect of the ion pair potentials [28,33,34].…”

Experimental study of the 61Σg+ state of the rubidium dimer

“…[21,, but the higher lying ion-pair states such as the 6 1 Σ + g state have not been observed experimentally. Highly excited 1 Σ states of alkali molecules are typically significantly perturbed and exhibit shelf regions and secondary wells due to couplings with other states as well as the ion-pair M + −M − * erahmed@temple.edu Coulomb potential (M − alkali atom) [66]. This gives rise to unusual properties including extremely long-range vibrations, large dipole moments, and a near-infinite manifold of vibrational states.…”