Collisional Orientation Transfer Facilitated Polarization Spectroscopy*

We report extensive collisional orientation transfer in V-type double-resonance polarization spectroscopy of the A$^{1}\Sigma _{u}^{+} \quad \sim $ b$^{3}\Pi _{u}$ complex of Rb$_{2 }$and Cs$_{2}$. Using this technique, in the Cs$_{2}$ case, we were able to observe a gap region in the A$\sim $b complex with poor Franck Condon factors (FCF) with the ground state. Since spectral congestion makes it difficult to find isolated pump transitions for a heavy molecule such as Cs$_{2}$, this technique allows us to observe many more rotational levels for each vibrational level than the customary strong $\Delta $J= $\pm $ 1 transitions. For probe transitions with very small FCF values we were able to observe angular momentum change with $\Delta $J$_{max}$ = 12, while in an analogous study of the Rb$_{2}$ A $\sim $ b complex of states, for transitions with larger FCF values, the maximum observed angular momentum change of the collisional satellite lines was $\Delta $J$_{max}$ = 58. Although collisional satellites lines were observed in polarization spectroscopy previously at a much higher pressure of several hundred Torr, our experiments were done at 1 Torr pressure without any loss in resolution.