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Raman Relaxation Times in Electronic Systems
Author(s) -
Shrivastava K. N.
Publication year - 1972
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.2220510138
Subject(s) - raman spectroscopy , ion , relaxation (psychology) , lattice (music) , phonon , condensed matter physics , series (stratigraphy) , physics , materials science , atomic physics , quantum mechanics , psychology , social psychology , paleontology , acoustics , biology
The theory of Raman relaxation is developed without the approximation of small wave vectors for the lattice phonons and it is shown that the accurate theory reduces into the known one if the expressions are expanded into infinite series and only the first term retained. The temperature dependence of electronic relaxation times is found to be more involved in the correct expressions than in the approximate ones. Eight different cases depending on the structure of energy levels are derived starting from a single formula. Four of these cases are new. Efforts are made to compare the theory with the experiments on Pr 3+ , Ce 3+ , Nd 3+ , Yb 3+ , and Mo 5+ ions. A new T 5 behaviour predicted for Kramers ions is apparently observed in Nd 3+ : LaCl 3 and Mo 5+ :TiO 2 and for the non‐Kramers Pr 3+ : LaCl 3 system. Faster temperature dependence than the usual T 9 one is predicted and probable indications of the same are noted on Ce 3+ , Nd 3+ , and Yb 3+ in CaWO 4 .