COHERENCE EFFECTS IN THE POLARIZATION OF LYMAN-ALPHA FLUORESCENCE FOLLOWING PHOTODISSOCIATION OF H-2 AND D-2

The polarization of the Lyman-alpha fluorescence following photodissoc iation of H-2 and D-2 into fragments in the 1s and 2l states has been determined as a function of the excess energy of the fragments. The pr edicted oscillations of the polarization as a function of excess energ y were clearly observed. In addition, the theoretical polarization was recalculated including the stronger B-B' coupling scheme as well as c ollisional effects on the polarization. The collisional effects includ e the quenching processes for H(2s) and H(2p) and disaligning collisio ns. The calculations reproduced the experimental data quite well givin g a cross section for the disaligning collisions of (1.0+/-0.2). 10(-1 4) cm(2) for H-2 and D-2 at a gas temperature of 137 K in the relative velocity range of 2 to 7 km s(-1). This can be considered as a proof of the theoretical predictions on the interference effects between the continua excited coherently. (C) 1995 American Institute of Physics.