Rotationally inelastic collisions of He and Ar with NaK: Theory and Experiment

Rotationally inelastic collisions of NaK (A 1Σ+) molecules with He and Ar have been studied. In the experiments at Lehigh, we use a pump-probe scheme (the probe is scanned over transitions to the 3 1Π state) with either polarization labeling (PL) or laser-induced fluorescence (LIF) spectroscopy. The pump laser excites a particular ro-vibrational level A 1Σ+ (v, J). We observe strong direct lines corresponding to transitions from the (v, J) level pumped, and weak satellite lines corresponding to transitions from collisionally-populated levels (v, J\u27=J + ΔJ). The ratios of satellite to direct line intensities in LIF and PL yield information about population and orientation transfer. A strong propensity for ΔJ= even transitions is observed for both He and Ar perturbs. Theoretical calculations are also underway for collisions in both the A 1Σ+ and X 1Σ+ states. For He-NaK we have calculated potential surfaces using GAMESS and carried out coupled channel scattering calculations of transfer of population, orientation, and alignment