Presently, known gas NPLs radiate in a wide band of the optical spectrum of 390­5,600 nm using approximately 50 transitions of atoms Xe, Kr, Ar, Ne, C, N, Cl, O, Hg, Cd, and I; the ions Cd+, Zn+, and Hg+; the molecule CO; and the molecular ion Nj.

3.1 IR Lasers Operating on Transitions of the Xe, Kr, and Ar Atoms

Nuclear-pumped lasers operating on transitions of Xe, Kr, and Ar atoms have been studied in greatest detail and have the maximal energy parameters of NPLs studied to date. Primarily, uranium fission products and nuclear reaction products 3He(n, p)3H were used to excite these lasers. Diagrams of the energy levels of atoms Xe, Kr, and Ar with laser transitions are shown in Fig. 3.1. Lasing occurred in the IR range of the spectrum, and the most intensive laser lines belong to the transitions nd-(n + 1)p of Xe, Kr, and Ar atoms (n = 5, 4, 3 for Xe, Kr, and Ar respectively).

Experimental investigations of NPLs operating on IR transitions of Xe, Kr, and Ar atoms in Russia were done chiefly at VNIIEF and VNIITF, and elsewhere at the Sandia Laboratories (United States).