Lasers operating on transitions of the I atom (A = 1.315 ^m) excited as a result of photodissociation of the molecules CF3I and C3F7I, or by transfer of energy to iodine atoms from metastable molecules of oxygen O2*(1A) + I(2P3/2)! O2*(3X) + I*(2P1/2), are well known as some of the most powerful sources of laser IR radiation [164, 165]. The literature reviewed several variations of excitation of the iodine laser by nuclear radiation: (a) formation of metastable molecules O2* (1Д) with subsequent energy transfer to iodine atoms [166, 167]; (b) formation of vibrationally excited molecules H2*(v > 2) in the mixture Ar-H2-I2 with subsequent transfer of energy to iodine atoms [168]; use of radioluminescent radiation of excimer molecules (KrF, XeBr, etc.) for photodissociation of molecules CF3I or C3F7I [169, 170].

Studies [166, 167] provide the results of experiments and theoretical investiga­tions into excitation by nuclear radiation of mixtures of He, Ne, and Ar with O2, aimed at determining the concentrations of O2*(^) necessary to achieve the laser threshold. Formation of O2*(^) can occur both during direct excitation of the oxygen-containing mixtures, and during photolytic decomposition of O3 by the radiation of excimer molecules, for example KrF. Pumping of an oxygen-iodine laser, or an Ar-H2-I2 laser [168], does not exist as yet.

A method of pumping an iodine laser using radioluminescent radiation of excimers is based on high conversion efficiencies of luminescence, which for many excimers is 20-30 % [170]. When the 3He-Xe-CHBr3 mixture is irradiated with the pulsed neutron flux of the TRIGA reactor, intensive radiation of the XeBr* molecules occurred (A = 282 nm), which then was used to photodissociate C3F7I [171, 172]. The conversion efficiency of luminescence for the XeBr* molecules (A = 282 nm) was around 1 %. The design of the laser cell is shown in Fig. 3.7. The power of the laser radiation at the line 1.315 ^m was not great: ~20 mW.