Energy Transfer by Resonance between TI+ Ions in KI Single Crystals

Energy transfer by dipole-dipole interaction between Tl + ions in KI single crystals was studied with several kinds of crystals different in Tl + concentration at low temperatures. Since two emission bands (2845 Å and 3044 Å) which appear under excitation at the B absorption band of Tl + ions overlap with the A absorption band of the ions, there is a possibility of energy transfer by resonance from excited Tl + ions to normal Tl + ions. The absorption coefficient of the A band and the emission bands produced by excitation at the B band were measured; and, thereby, the critical transfer distance R 0 was obtained from Dexter's formula. Furthermore, the decay curves of the donor emissions were measured by a pulse method and their shapes were analyzed with Eisenthal and Siegels's theory. The values of R 0 thus obtained for 2845 Å and 3044 Å emissions were 35 Å and 26 Å, respectively. They were in good agreement with those obtained from Dexter's formula, that is, 33 Å and 24 Å respectively.