Relaxation dynamics of electronic excitations in CaWO₄ and CdWO₄ crystals studied by femtosecond interferometry technique

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• 作者：V. Nagirnyi ; G. Geoffroy ; R. Grigonis ; S. Guizard ; M. Kirm ; A. Kotlov ; L.L. Nagornaya ; M. Nikl ; V. Sirutkaitis ; S. Vielhauer
• 关键词：Tungstates ; Excitons ; Time-resolved interferometry
• 刊名：Radiation Measurements
• 出版年：2010
• 出版时间：March-July 2010
• 年：2010
• 卷：45
• 期：3-6
• 页码：262-264
• 全文大小：276 K

文摘

The relaxation of electronic excitations in CdWO₄ and CaWO₄ crystals was studied using the method of time-resolved interferometry with 100-fs temporal resolution at temperatures 15–295 K. The electronic system was excited in the one-photon and two-photon regime within the excitonic band in CaWO₄ and in the electron-hole continuum in CdWO₄. Immediate trapping of charge carriers was detected under pumping in the excitonic band of CaWO₄. This result is in agreement with decay kinetics measurements with nanosecond time resolution under direct creation of excitons by 100-fs laser pulses. Fast relaxation of charge carriers followed by formation of excitons was observed in CdWO₄. The comparison with previous work allows suggesting the formation of bulk excitons and surface-perturbed excitons in the multi-photon and one-photon regime. The corresponding models of self-trapped exciton creation in tungstate crystals are discussed.