| Abstract: | The processes of creating and transforming electronic color centers in an LiF crystal irradiated with a nanosecond electron
pulse are investigated using pulse spectrometry with nanosecond resolution for times in the range 10−8 to 105 sec. It is shown that the thermally activated mechanism of forming Frenkel pairs in the 12–200 K range consists of successively
creating exciton states, as the temperature rises, having different degrees of spatial separation of the electron and hole
components. It is concluded that the structure of self-trapped excitons evolves as a function of temperature and time, and
that this evolution commences for any alkali halide crystal with the creation of self-trapped excitons ofD
2h point symmetry at 4 K. It is established that the interaction of electronic excitations with electronic color centers changes
the properties of both the electronic excitations themselves and the color centers. In a crystal containing neutral electronic
centers there is a fall in the yield of self-trapped excitons and Frenkel pairs and an increase in the contribution of the
radiative channel for loss of the irradiation energy by the color centers. A mechanism is proposed for exciting luminescence
of electronic color centers. It is established that short-lived irradiation-induced states exist, in particular a change in
the spin state or in just the energy state of a center in the irradiation field, and that the appearance of these states changes
the efficiency and directivity of the charge evolution of the electronic color centers.
State Architectural Building Academy, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 57–75,
November, 1996. |
