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Luminescence of CsCl: Tl Single Crystals
Author(s) -
Nagirnyi V.,
Zazubovich S.,
Jaanson N.
Publication year - 1993
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221750113
Subject(s) - excited state , luminescence , atomic physics , metastability , chemistry , triplet state , ion , population , crystal (programming language) , tetragonal crystal system , molecular physics , materials science , physics , crystal structure , crystallography , demography , optoelectronics , organic chemistry , sociology , computer science , programming language
Spectral, polarization, and kinetic characteristics of CsCl:Tl luminescence are studied between 4.2 and 350 K. The A x band at 3.88 eV and the A T band at 3.65 eV are observed in the triplet emission spectrum of Tl + centres. It is shown that in the triplet relaxed excited state (RES) the trigonal (X) minima are of higher energy than the tetragonal (T) ones. The symmetry of both the emitting and the metastable states in each (X or T) minimum is the same, and in many respects their structure is similar to that of other n s 2 ions in alkali halides. However, some peculiarities are observed in the luminescence characteristics of CsCl:Tl crystals (e.g. very small quantum efficiency of triplet emission at excitation in high‐energy absorption bands; population of the lower (T) minima mainly in the process of vibronic relaxation in the triplet excited state; too large polarization degree of the slow decay component of the A x emission, exceeding 1.5 times its theoretical limit; large difference in the spin‐orbit splitting energies δ of the triplet RES in the × and the T minima as well as in radiative decay probabilities y 1 of their metastable states; the absence of an off‐centre displacement of the excited Tl + ion from the crystal lattice site, etc.). Possible reasons for these features are discussed.