The quasi-stationary and transiont spectra of the nonequilibriurn electron-hole plasma (EHP) emission are investigated in CdSe crystals. A broadening of the low-energy side of the luminescence band due to the heating of longitudinal-optical (LO) phonons is established. A slow stage of the EHP energy relaxstion with a time constant of 150 ps is observed and referred to the accumulation of decay products of nonequilibrium LO phonons in the narrow interval of the kspace. A model of the two-stage relaxation of the phonon subsystem in a photoexcited semiconductor is used to calculate the power of energy-loss in hot EHP and the nonequilibrium LO phonon distribution. I?C!CJlCXOBaHLI KBa3MCTaqUOHaplfblC U pa3peUICHHhle BO RpCMeHU CneKTpbI H33yqCHUfl HepaRHOBCCIIO# %JIeKTpOHHO-~bIpO~HOfi nJIa3MhI (aan) B KpMCTajlJMX CdSe. YCTalfOBJle-HO, 9TO @IUIi~iOBOJIHOBbIfi Kpaa iIO.lOCbl JIIOMHHeCUCt WMM 3,4n yUIUpHeTCJ3 113-3a pa30rpesa npoaonrm,Ix onTuqecmx (LO) @oHoiroR. 0611apyme~ uenneaimfi man penaKcaiww nHeprua 32n c nocTomrHv8 Rpeueiiu 150 ps, IiOTOPbIfi oTHeceIi I( iraKonneimm npoaymon pacIra,la HepauiroriecHux LO @OHOHOB R ~3~0 t h 06nac~u k-IIpOCTpaHCTRa. Ha OCliOBe MOileJM ,mYX3TaIIHOfi peJaKCaUMU (POHOHIIOfi nOJCHCTeMb1 (POTOB036YiKlWH-IIOI'O nOJIyIIpOROaHMKa PaCCqMTaHa MOUHOCTL 3HCpreTHqCCKUX IIOTepb rOpHqf fi 3fin M pacirpeneneme HepaBHvnecHr,Ix LO ~O H O H O B .

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AhslraeC me energy rtlaxation of a photogenerated elenron-hole plasma is investigated in highly excited CdS at m m temperature using time-resolved luminescence in lhe picosecond legime. It is established that the non-equilibrium camer acess energy dissipation process exhibils a two-stage pattern with increasing excitation density. These stages refled the sequential process of anharmonic decay o[ the non-equilibrium phonon system generated during plasma maling. Experimental data are explained in terms of the kinetic model, taking into aocount two generations of non-equilibrium phonons.A high excitation level is shown to h a crucial condition for the manifestation of a seeond-generation phonon bottleneck in hot-carrier energy relaxation.

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