Mechanisms of ionization of F-2-centers in laser media on the basis of LiFcrystals

F-2 color centers with a superhigh concentration (5000-cm(-1) absorption co efficient at 450 nm) were formed by high-density electron beams in a layer of LiF crystals of micrometer thickness. The F-2-centers excited by high-po wer nanosecond wide-band optical pulses (the "soft" pumping regime) efficie ntly amplified the laser radiation and showed high stability under these co nditions. A low stability of F-2-centers to laser radiation (the "hard" exc itation regime) is explained by the dissociation of (F-2(+), F-) pairs indu ced by two-step ionization of F-2-centers: (2hv > 4.5 eV) --> F-2 --> (F-2) * --> F-2(+) + e; F + e --> F-; F-2(+) + F- --> 3F. (C) 2000 MAIK "Nauka/In terperiodica".