Excited States of theFCenter

Various $L$ bands have been measured in KCl and KBr x rayed at liquid-helium temperature and in KCl: H x rayed at room temperature. These results argue against the suggestion that the $L$ bands arise from complexes involving $F$ centers and support the argument that the $L$ bands arise from the $F$ center itself. A charge-transfer model of the $L$ bands is proposed in which the transitions correspond to a combination of transferring the $F$-center electron to a neighboring alkali ion and raising the resulting alkali atom to one of its excited states.