Non-thermal Doppler-broadened Lyman-? line shape in resonant dissociation of H2

The detailed Lyman-? emission line shape after resonant dissociation and excitation of H2via collisions with Ne excimer molecules has been determined (Ne*2+ H2? 2Ne + H + H*(n= 2)). Pressure effects due to the high Ne pressure, required for efficient excimer formation, decrease the effective lifetime of the hydrogen excited state. The reduced effective lifetime significantly reduces the average number of elastic collisions experienced by the excited hydrogen atom before radiative decay. Excess energy imparted to the excited-state hydrogen atom by the Ne excimer, in the dissociative excitation collision, produces a non-thermal Doppler-broadened emission line shape. The full width at half maximum (FWHM) is 3.85 pm and the effective lifetime of the n= 2 state is estimated to be 14 ps at a Ne pressure of 1 atm. Results are obtained from pressure-dependent measurements of the Balmer-? absorption line shape using laser spectroscopy.