POLARIZATION OF ATOMIC POTASSIUM FLUORESCENCE EXCITED BY LASER PHOTODISSOCIATION OF K2

$^{1}$ R. J. Van Brunt and R. N. Zare, J. Chem. Phys. 48, 4304 (1968). $^{2}$ J. Vigue, J. A. Beswick and M. Broyer, J. de Physique 44, 1225 (1983).Author Institution: Iowa Laser Facility, University of IowaA tunable dye laser was used to excite $K_{2}$ from the ground $X(^{1}\Sigma^{+}_{g})$ state into the continuum of the $B(^{1}\Sigma_{u})$ state. This results in dissociation of the molecule producing an excited $K {^{2}}P_{3/2}$ atom which fluoresces. By monitoring the atomic $D_{2}$ fluorescence under these molecular beam (collision-free) conditions, we were able to measure the pure bound-free absorption profile. At the same time, the polarization of the atomic fluorescence was measured for different laser excitation frequencies. We believe this to be the first observation of a large variation in the polarization, ranging from $15 \pm 2\%$ to $-6.3 \pm 0.4\%$ as a function of laser excitation wave-length. The results are explained a) using the theory of Van Brunt and Zare1, which predicts a maximum polarization of 14.3\% (axial recoil) and a minimum of -7.7\% (transverse recoil) and b) the Rotating molecule $theory^{2}$ where the polarization is a function of the angle of rotation of a half collision. Classical, semiclassical and quantum-mechanical calculations in the $K_{2}$ case were also performed and a comparison with the experimental results is given