ALIGNMENT OF HG-AR VAN-DER-WAALS MOLECULE PHOTOFRAGMENTS FOLLOWING PHOTODISSOCIATION

We have measured the alignment of the photofragments produced by photo dissociation of Hg-Ar van der Waals molecules using light around 253.7 nm. The molecules are produced in the XO+ ground state in a supersoni c expansion. Tunable laser light close to the Hg 6 S-1(0)-6 P-3(1) tra nsition is then used to excite the molecule to the B1+/- state, in whi ch it dissociates. The alignment of the resulting Hg(P-3(1)) asymptoti c atoms is probed by tuning a delayed second laser to the 435.8 nm Hg 6 P-3(1)-7 S-3(1) atomic transition and monitoring the subsequent fluo rescence on the 7 S-3(1)-6 P-3(2) transition around 546.1 nm. These me asurements have been made, we believe for the first time, as a functio n of dissociating energy from very close to threshold to higher energi es. The alignment shows a significant rise with increasing photon ener gy in line with a semiclassical picture of orbital locking at lower en ergies and rapid decoupling at higher energies. The results exhibit go od agreement with the results of a fully quantum mechanical theory of the system.