Polarization of the Absorption Bands Due to the STE in NaCl, KCl, KBr and RbBr Crystals

Degree of polarization of the σ and π emissions has been measured to determine the polarization of the absorption bands due to the STE in NaCl, KCl, KBr and RbBr crystals under double excitation by a pulsed electron beam and a ruby laser. (1) The lowest, (2) the second lowest and (3) the third lowest energy absorption bands in near infrared region due to the STE are (1) π-polarized, (2) σ-polarized and (3) slightly σ-polarized (1) in NaCl and KCl, (2) in KBr and (3) in RbBr, respectively. The lowest band in NaCl and KCl and the second lowest one in KBr are tentatively attributed to the transition of 3 Σ + u (σ u , \(1s{σ}g){→}³g(σᵤ\), 2 p π u ) and 3 Σ + u (σ u , 1 s σ g )→ 3 Σ + g (σ u , 2 p σ u ).