Lyman-alpha emission via resonant energy transfer

Very intense hydrogen Lyman-alpha (2p P-2(0) --> 1s S-2) light emission (lambda = 121.6 nm) is observed from neon gas near atmospheric pressure containing small admixtures (per mil) of hydrogen when this gas mixture is excited by ionizing particle beams. A DC beam of 15 keV electrons or a pulsed beam of 100 MeV S-32 ions were used in different experiments for excitation. A collisional energy transfer rate constant from neon to H* of (3+/-1) x 10(-11) cm(3) s(-1) has been measured using time-resolved optical spectroscopy on the Lyman-alpha line. Conversion efficiencies of particle beam power into Lyman-alpha light of the order of 10% have been observed. No other significant radiation was emitted in the entire VUV, UV and visible spectral region. In particular, no other hydrogen lines are observed under these conditions. The selective excitation of the H(2p) level is interpreted as arising from a resonant energy transfer between Ne-2* excimers and hydrogen molecules.