Influence of Molecular Gases on the Lasing on the Self-Terminating $He~\left(2^{1}P_{1}^{0}-2^{1}S_{0}\right)$ Transition

Excitation with single and dual electron-beam pulses was used to investigate into the lasing on the self-terminating He (2¹P₁⁰-2¹S₀) transition in mixtures of helium with various molecules. In pure helium the maximum lasing duration was found to be equal to 50 ns, this time being fairly well coincident with the calculated lasing duration. Restoration of lasing in the second pulse was observed following a time Δt_min >; 1.25 μs. Foreign molecular species admixed to helium enhance the relaxation rate of the metastable He(2¹S₀) state, thus making the time Δtmin shorter until the pulses finally merge together. In the mixtures of helium with NH₃ and H₂O excited with 650-ns electron-beam pulses, the lasing duration of 600 ns was observed. Such duration indicates realization of a collisional quasi-continuous lasing mode.