Experimental mapping of the absolute magnitude of the transition dipole moment functionμe(R)of theNa2A Σ1u+−X Σ1g+transition

Abstract

The absolute magnitude of the transition dipole moment function ${\ensuremath{\mu}}_{e}(R)$ of the $A\text{ }{^{1}\ensuremath{\Sigma}}_{u}^{+}\ensuremath{-}X\text{ }{^{1}\ensuremath{\Sigma}}_{g}^{+}$ band system of ${\text{Na}}_{2}$ was mapped experimentally over a relatively large range of internuclear distance $R$. The transition dipole moment matrix element of a set of rovibrational transitions between the $A\text{ }{^{1}\ensuremath{\Sigma}}_{u}^{+}$ and $X\text{ }{^{1}\ensuremath{\Sigma}}_{g}^{+}$ states was measured using the Autler-Townes effect. By employing the $R$-centroid approximation, or a fit to a polynomial function involving higher order $R$ centroids, ${\ensuremath{\mu}}_{e}$ as a function of the internuclear distance was obtained. These Autler-Townes effect based measurements yield the absolute magnitude of ${\ensuremath{\mu}}_{e}$, which can be used to test ab initio theoretical transition dipole moment functions or to ``normalize'' experimental transition moment functions obtained from intensity measurements, which in general give only the relative behavior of ${\ensuremath{\mu}}_{e}(R)$.