Manifestations of the free–two-site exciton mixing in luminescence excitation spectra of doped crystals

✍ Scribed by A.M Ratner

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 235 KB
• Volume: 265
• Category: Article
• ISSN: 0375-9601
• DOI: 10.1016/s0375-9601(99)00859-2

✦ Synopsis

It is known that in rare-gas and alkali-halide crystals the excitons exist both in a free state and in the form of excimer two-site quasi-molecules. Due to mixing of the states of two types, vibrational levels of excimer quasi-molecules turn to narrow subbands. Thermal relaxation of an exciton can occur along the free-exciton dispersion branch or via consecutive transitions between the subbands, an exchange of excitations between these relaxation paths being possible. Heavy two-site excitons, moving in a narrow subband, are easily localized on shallow traps, present in a real crystal, or near impurity centers. Their trapping sections, as well as the initial type of photoproduced excitons, depend on excitation energy. Therefore, the distribution of luminescence intensity between the free-exciton, two-site exciton and impurity bands essentially depends on excitation energy. The derived regularities are in a good qualitative agreement with available experimental data.