De-excitation of H(2p) in a collision with a H2 molecule

The velocity assigned experiment of the collisional de-excitation of a H(2p) atom by a H2 molecule is demonstrated by measuring the time-dependent intensity of Lyman-α radiation emitted in the photodissociation of H2 using a pulsed synchrotron radiation in the vacuum ultraviolet region. Observed decay rates of Lyman-α radiation have given the rate constant or cross section for the de-excitation of H(2p) by H2. The cross section is about 3×10−14 cm2 in the region of the collisional velocity between 4.6×105 and 12×105 cm/s, which is several times larger than that for the H(2s) de-excitation. It has been concluded that the l-changing collision is quite important in the de-excitation of H(2p) by H2.