LYMAN-ALPHA EMISSION VIA RESONANT ENERGY-TRANSFER

Very intense hydrogen Lyman-alpha (2p P-2(0) --> 1s S-2) light emissio n (lambda = 121.6 nm) is observed from neon gas near atmospheric press ure containing small admixtures (per mil) of hydrogen when this gas mi xture is excited by ionizing particle beams. A DC beam of 15 keV elect rons or a pulsed beam of 100 MeV S-32 ions were used in different expe riments for excitation. A collisional energy transfer rate constant fr om 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. Conversio n efficiencies of particle beam power into Lyman-alpha light of the or der of 10% have been observed. No other significant radiation was emit ted in the entire VUV, UV and visible spectral region. In particular, no other hydrogen lines are observed under these conditions. The selec tive excitation of the H(2p) level is interpreted as arising from a re sonant energy transfer between Ne-2 excimers and hydrogen molecules.