ISOELECTRONIC TRAP IODINE IN AGBR

Iodine in AgBr behaves as an isoelectronic trap with the hole being bound first. The bound-exciton zero-phonon photoluminescence line is split by exchange into an A-line and a B-line separated by 0.1 meV. The Zeeman splitting at H=80 kG is isotropic in agreement with iodine being a substitutional point-like impurity in AgBr. In the low-temperature limit optic and acoustic phonons contribute to the phonon side wing with nearly the same coupling strength. At temperatures below 10K, up to n=11 phonons are observed in the phonon side band. The authors present experimental evidence that these are due to the emission of n optic phonons which, for n>3, are statistically independent. A multiphonon model which neglects the k dependence of transition rates is introduced; however, the model is useful only qualitatively.