The Jahn-Teller effect is invoked to explain the fine structure (isolated zero-phonon lines) observed in both the infrared emission and absorption spectra of substitutional Cr2+ impurities in ZnSe and ZnS. The ground 5D2 term of Cr2+ is split by crystal field into a 5T2 ground multiplet and an excited 5E multiplet. We look at transitions among levels belonging to these two multiplets, which happen to be in the near infrared region. Spin-orbit and spin-spin interactions are taken into account. The Jahn-Teller coupling is introduced as a linear coupling considering both ϵ and τ2 phonons. The Lanczos-recursion procedure with a proper choice of the initial state is used to calculate the vibronic functions and energies. It is found that ϵ modes only lead to intensities that do not agree well with those of the zero-phonon doublet observed both in emission and absorption in the cases of ZnS and ZnSe, while τ2 modes give a good explanation of transition energies and transitions strengths in the same cases. A discussion of the relatively high strength of the vibronic coupling for Cr in comparison with other impurities in the same compounds is also included.

Bevilacqua, G., L., M., E. E., V., & O., M. (2004). Jahn-Teller effect in the emission and absorption spectra of ZnS:Cr^2+ and ZnSe:Cr^2+. PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS, 70(7) [10.1103/PhysRevB.70.075206].

Jahn-Teller effect in the emission and absorption spectra of ZnS:Cr^2+ and ZnSe:Cr^2+

BEVILACQUA, GIUSEPPE;
2004

Abstract

The Jahn-Teller effect is invoked to explain the fine structure (isolated zero-phonon lines) observed in both the infrared emission and absorption spectra of substitutional Cr2+ impurities in ZnSe and ZnS. The ground 5D2 term of Cr2+ is split by crystal field into a 5T2 ground multiplet and an excited 5E multiplet. We look at transitions among levels belonging to these two multiplets, which happen to be in the near infrared region. Spin-orbit and spin-spin interactions are taken into account. The Jahn-Teller coupling is introduced as a linear coupling considering both ϵ and τ2 phonons. The Lanczos-recursion procedure with a proper choice of the initial state is used to calculate the vibronic functions and energies. It is found that ϵ modes only lead to intensities that do not agree well with those of the zero-phonon doublet observed both in emission and absorption in the cases of ZnS and ZnSe, while τ2 modes give a good explanation of transition energies and transitions strengths in the same cases. A discussion of the relatively high strength of the vibronic coupling for Cr in comparison with other impurities in the same compounds is also included.
Bevilacqua, G., L., M., E. E., V., & O., M. (2004). Jahn-Teller effect in the emission and absorption spectra of ZnS:Cr^2+ and ZnSe:Cr^2+. PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS, 70(7) [10.1103/PhysRevB.70.075206].
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11365/21661
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