Pulsed lasing at electron-vibration transitions of the first negative system of the molecular ion N2+ (X = 427.8 nm) with pumping of a high-pressure He-N2 mixture with an electron beam with a duration of 20 ns was obtained in 1974 [146]. Later on, with pumping of the mixture He-N2-H2 (X = 391.4; 427.8 ns) with an electron beam with a duration of 0.7 qs, it was possible to realize a quasi-CW operating mode using hydrogen to quench low laser levels: N2+(X) + H2! N2H+ + H [147]. The efficiency of the laser was ~1 % at a specific power deposition q = 5-10 kW/cm3.

The possibility of pumping this laser with nuclear radiation was examined in study [148]. As a result of calculating the kinetics of plasma processes in the mixture He-N2-H2, it was concluded that it was possible to achieve lasing at X = 391.4 and 427.8 nm for q = 1-3 kW/cm3, which is quite attainable in experi­ments on fast reactors EBR-L and SPR III.

Soon afterward, the same authors used an EBR-L setup to obtain lasing at the 391.4-nm line when the He-N2-H2 mixture was excited by uranium fission frag­ments with a output power of ~10 W and nI~0.01 % [149]. This laser became the first NPL radiating in the UV range of the spectrum. Later on, in experiments with the EBR-L reactor, lasing was also registered at X = 427.8 nm of the ion N2+ [150]. For an optimal mixture of He-N2-H2 at pressures of 3.5-5 atm (partial pressures of nitrogen and hydrogen 3-10 Torr), at lines 391.4 nm and 427.8 nm, laser efficiencies of 0.3 % and 0.2 %, respectively, were obtained. Confirmation of these results was obtained in experiments [151] with a BARS-6 pulsed reactor, in which a He-N2-H2 mixture was excited by uranium fission fragments. Lasing was observed at the lines 391.4 and 427.8 nm for substantially lower specific threshold power depositions of 50-60 W/cm3 (nI ~0.1-0.2 %).