The emission spectra and the excitation spectra of various emissions were measured in LiF crystals at 9K using vacuum ultra-violet radiation of 10 to 33eV. In contrast to the luminescence of self-trapped excitons (3.4eV), the efficiency of several extrinsic emissions (4.2, 4.6 and 5.8eV) was very low in the region of an exciton absorption (12.4–14.2eV). A single exciting photon of 28–33eV was able to create a primary electron–hole (e–h) pair and a secondary exciton. The tunnel phosphorescence was detected after the irradiation of LiF by an electron beam or X-rays at 6K, and several peaks of thermally stimulated luminescence at 12–170K appeared at the heating of the sample. It was confirmed that the thermally stimulated luminescence at 130–150K was related to the diffusion of self-trapped holes (VK centers). The thermally stimulated luminescence peak at ~160K was ascribed to the thermal ionization of F' centers. The thermally stimulated luminescence at 20–30K and 50–65K was caused by the diffusion of interstitial fluorine ions (I centers) or H interstitials, respectively. The thermally stimulated luminescence peak at ~13K, the most intense after electron or x-irradiation, cannot be detected after LiF irradiation by vacuum ultra-violet radiation, selectively forming excitons or e–h pairs. The creation of a spatially correlated anion exciton and an e–h pair was needed for the appearance of this peak: an exciton decays into an F–H pair, a hole formed a VK and an electron transformed H into I (an F–I–VK group was formed) or an F center into a two-electron F' center (an F'-H -VK group). The analysis of the elementary components of the 9–16K thermally stimulated luminescence showed that a phonon-induced radiative tunnel recombination of F'–VK (5.6eV), F–H (~3eV) and F–VK (3.4eV) occurred within these groups.

Low-Temperature Excitonic, Electron–Hole and Interstitial-Vacancy Processes in LiF Single Crystals. S.Nakonechnyi, T.Kärner, A.Lushchik, C.Lushchik, V.Babin, E.Feldbach, I.Kudryavtseva, P.Liblik, L.Pung, E.Vasilchenko: Journal of Physics - Condensed Matter, 2006, 18, 379-94