Measurement of the Na2 51Σg+→A1Σu+ and 61Σg+→A1Σu+ transition dipole moments using optical-optical double resonance and Autler-Townes spectroscopy.

Accurate knowledge of transition dipole moment matrix elements is crucial since important parameters associated with the interaction of light with matter, such as emission and absorption line intensities, lifetimes, and Einstein coefficients, depend on these matrix elements. We report here an experimental study of the Na2 51Σg+↔A1Σu+ and 61Σg+↔A1Σu+ electronic transition dipole moments and their dependence on internuclear distance. We have measured absolute transition dipole matrix elements for ro-vibrational transitions of the Na2 51Σg+↔A1Σu+ and 61Σg+↔A1Σu+ electronic transitions using Autler-Townes and optical-optical double resonance spectroscopy, and we compare the results to ab initio theoretical values [A. Sanli et al., J. Chem. Phys. 143, 104304 (2015)].