Induced infrared absorption due to polarons generated by band-to-band light has been studied in AgBr and AgCl at low temperatures. Strong narrow zero-phonon lines with sideband structure are observed. The positions of the sharp far-infrared absorption lines indicate that exciton or bound polaron states of large radius are involved. The results are compared with a nonadiabatic theory for bound polarons. An unusual and extremely slow logarithmic decay of the induced absorption is observed, together with a logarithmic dependence of the induced absorption on the generating intensity. A model consisting of separated electron and hole polaron pairs, as well as alternative models, is discussed.

• Received 30 December 1968

DOI:https://doi.org/10.1103/PhysRev.181.1241