  A full quantum mechanical theory for the spontaneous emission from excitons
simultaneously coupled to electronic excitations and anharmonic phonons in
solid is developed. Origin of detailed structures, such as zero-phonon line
splitting, Fano lineshape near one phonon sideband, strong second-order phonon
Stokes line, asymmetric phonon anti-Stokes lines, and two-electron satellites
as well as their phonon replicas recently revealed in the low-temperature
photoluminescence of ZnO, has been identified by quantitative calculations from
the theory.
