The exciplex lasers are now the most powerful among plasma lasers from visible to VUV range. The lasers on the exciplex molecules KrF ((lambda) equals 249 nm), ArF ((lambda) equals 193 nm), XeF ((lambda) equals 351, 353 nm) are most advanced. The operating transition of this laser is B yields X. The lower (ground) operating term X is the repulsive or weak-coupled one. The highest efficiency (10%) have KrF-laser and may be ArF-laser. The XeF-laser efficiency is not so high (approximately 3%), but this laser is of interest because it has the lowest threshold of pumping among exciplex lasers. Therefore, the opportunity of nuclear pumping of XeF-laser is under discussion. The X term have in XeF molecule a rather deep well. This peculiarity leads to more strong gas temperature dependence and not high efficiency. It must be mentioned that in the models of the XeF-laser developed up to today, the temperature dependence of plasma-chemical reaction rates, and its influence on laser output is not considered in details. Besides, the only effective operating transition, not the lasing on two separate transitions ((lambda) equals 351 and 353 nm) was considered in most papers.