Energy-Dependent Photodissociation Dynamics Probed by Fluorescence Polarization

A linearly polarized tunable cw dye laser was used to excite ${\mathrm{K}}_{2}$ from the ground $X^{1}\ensuremath{\Sigma}_{\mathrm{g}}^{+}$ state into the continuum of the $B^{1}\ensuremath{\Pi}_{\mathrm{u}}$ state. Resulting photodissociation produces excited atomic $\mathrm{K}(^{2}P_{\frac{3}{2}})$ which radiates on the ${D}_{2}$ line. As the laser is tuned through the molecular bound-free absorption profile, we have observed a large variation in the polarization of atomic fluorescence ranging from plus 15% \ifmmode\pm\else\textpm\fi{} 2% to minus 6.3% \ifmmode\pm\else\textpm\fi{} 0.4%. We believe this variation can be explained in terms of molecular rotation during dissociation. These results are consistent with a completely adiabatic model for the dissociation.