Lymanhyphen;agr; Fluorescence from the Photodissociation of H2

摘要

Photodissociation and fluorescence cross sections for H2have been measured from 860 to 700 Aring; by observing the Lymanhyphen;agr;photons emitted at 90deg; to an incident photon beam. The photodissociation quantum efficiency was found to be unity from 850 Aring; to the photoionization threshold at 804 Aring; and about 10percnt; at shorter wavelengths. By observing the fluorescence radiation as a function of decreasing pressure, it was determined that most of the excited H atoms were formed in the metastable2sstate and that the Lymanhyphen;agr;emission results primarily from collisional quenching. The ratio of the collisional cross section with and without Lymanhyphen;agr;emission was measured for different relative velocities and was found to increase appreciably with increasing velocity.