Two-photon spectroscopy of ions in crystals: Cu+ and Ag+ in the alkali halides

Abstract

The two‐photon (TP) spectra of the Cu⁺ and Ag⁺ impurities in some alkali chloride hosts have been obtained; here the ion is situated in a nearly octahedral chloride environment. Since the d→s transitions observed in the near UV are electronically allowed in TP spectroscopy (δ=3 gm), a simple theory of the polarization studies, in conjunction with the DV‐Xα computer code led to a definitive characterization of the ¹E_g, ¹T_2g crystal field splitting of the d⁹s excited state. We also obtained evidence of the Jahn–Teller effect in the ¹E_g(d⁹s) state as well as a good understanding of the mixing of the ¹E_g, ¹T_2g states resulting from the dynamic and static displacements of Cu⁺. The absolute value of the two‐photon cross section was measured and compared to a calculated value.