Intrinsic Luminescence of RbI and KI at 10°K

Emission and excitation spectra for the intrinsic luminescence of RbI and KI have been measured at 10°K and compared with the exciton spectra of the two materials. Two emission bands appear at 3.31 and 4.15 eV for KI, and three for RbI at 2.64, 3.15, and 3.95 eV. Each band has a distinctive excitation spectrum. The high-energy band in each material appears to be connected either with interband transitions or excitation of the $n=2\mathrm{}$ Wannier exciton line, while the low-energy emission is associated with absorption in or near the first exciton line. Evidence is given for the existence of a third component of the Wannier exciton series observed recently by Fischer and Hilsch.