STACKING-FAULT EXCITONS IN AGBR MICROCRYSTALS WITH TWIN PLANES

The visible emission and excitation spectra of AgBr microcrystals cont aining single and parallel double twin planes has been obtained. A ban d at 462.28 nm (2.6813 eV) is observed in the excitation spectrum. Thi s feature is about 2.5 meV below the indirect exciton band edge. Coinc ident emission features are observed. The band in the excitation spect rum of microcrystals with two parallel twin planes is often split into a doublet with splittings between 1 and 2 meV. The new band is assign ed to an exciton created at a stacking fault and the splittings are th ought to be due to tunnelling of the exciton between proximate twin pl anes.