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The resonant secondary radiation spectrum of impurity centres in crystals is studied on the basis of a second-order approximation for the interaction between the electromagnetic field and the material. It is shown that for the case of excitation in the phonon wing of the absorption band, the main part of the secondary radiation represents the ordinary luminescence. The spectrum also contains Rayleigh and Raman scattering which is considerably weaker (by about four orders of magnitude). Formulas are obtained for the intensities of Rayleigh-and Rsman scattering ; particular consideration is made for the case of large Stokes' losses. It is also shown that excitation in the region of the pureelectronic line yields a spectrum consisting of the Rayleigh and the pure-electronic line, and the phonon wing of the luminescence. PaCCMOTpeH CIIeKTp pe30HaHCHOrO BTOPH'IHOrO CBeqeHUR KPUCTanJIOB, IIC-XOAR U 3 (POpMyJIbI BTOpOrO IIOpHnHa IIO B3aUMO~efiCTBUIO 3JIeKTPOMarHIlTHOl'O IIOJIR C BeweCTBOM. nOKa3aH0, 'IT0 B CJIy'Iae B036ymAeHHs B (POHOHHOM KpbIJIe IIOJIOCbI IIOrnOweHPiH OCHOBHOB 'IaCTbIO BTOPUYHOrO CBeqeHUfi RBJIReTCFI JIIOMU-HeCUeHUUII. OAHOBpeMeHHO CIleKTp COAepHCHT Il CyUeCTBeHHO 6onee cna6are RJIH UHTeHCUBHOCTefi PeJIeeBCKOrO II KOM6EIHaUHOHHOrO PaCCeRHElfi. Oco6oe BHUcnysae B036YHCAeHWH B o6nac~1l 'IUCTO-3jIeKTPOHHO~ JIUHUU CIIeKTp COCTOIlT U3 PeJIeeBCKOfi U 9EiCTO-3JIeKTPOHHOfi JIHHIld U (POHOHHOI'O KpbIJIa JIH)MUHeCUeHUUU. (B 2 104 pa3) peneeBcKoe ri KOM6IlHaqHOHHOe paccesaas. rIonyseHM @OPMYJIEJ Mame yneneHo cnysam 60nbm~x CTOKCOB~IX noTepb. r I o~a 3 a~o TaKme, w o B

A new method of considering quadratic vibronic interactions and deviations from the Condon approximation in resonance Raman scattering (RRS) is proposed. The method is used for the generalization of the transform law between absorption and Raman excitation profiles, derived earlier for a basic model. In the case of arbitrary mixing of modes with similar frequencies, a simple generalization of the transform law for first-order RRS is obtained. For an arbitrary change of frequencies without mode mixing the transform law for the nth-order RRS is given. The equations are valid for an arbitrary number of modes and also take temperature effects into account.

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For a n impurity centre the resonant secondary radiation spectrum, consisting of luminescence, Raman scattering, hot luminescence, and interference terms, is studied a t low temperatures using the model of one local or pseudolocal mode, active in the electronic transition and taking into account the change of the equilibrium position and frequency of this mode. It is shown that the latter plays an essential role in the problem of the classification of the resonant Raman scattering and hot luminescence. The anti-Stokes region of the spectrum is analysed in detail for three cases of excitation: monochromatic, "white", and intermediate excitation. The influence of the interference of different relaxation channels on the intensity, width, and shape of the lines is considered.

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In multi-mode systems with a degenerate excited electronic state, resonance Raman scattering (RRS) can be effectively examined by the Fourier amplitude formalism, where RRS amplitudes are described by the Fourier transforms of phooon correlation functions. Model calculations of REPs of both totally and non-totally symmetric modes have been carried out in the case of a weak vibronic coupling to off-diagonal modes. The cakulations demonstrate a high sensitivity of RRS to the Jahn-Teller effect for the vibrations of both the discrete and the continuum spectrum.

No abstract