Anomalous 10-ns emission inCe3+-dopedCs3

An emission at 281 nm with a 10.5 ns single exponential decay and a highly selective, narrow excitation region between 202 and 211 nm has been observed for ${\mathrm{Ce}}^{3+}$ doped in ${\mathrm{Cs}}_{3}{\mathrm{LuCl}}_{6}.$ Wavelengths between 50--200 nm and longer than 215 nm have zero excitation efficiency. Excitation and emission spectra of ${\mathrm{Cs}}_{3}{\mathrm{LuCl}}_{6}:{\mathrm{Ce}}^{3+}$ in the 10--300 K temperature range were excited by pulsed synchrotron radiation between 50--335 nm. In addition to this new emission, the conventional ${\mathrm{Ce}}^{3+}$ doublet emission from the lowest $5d$ level to the ${}^{2}{F}_{5/2}$ (368 nm) and ${}^{2}{F}_{7/2}$ levels (400 nm) of the ${4f}^{1}$ configuration is observed. Autoionization of the $5d$ electron to conduction band states followed by the direct transition to the ${}^{2}F$ levels is proposed to explain the 281 nm emission and to explain the absence of emission under across bandgap excitation.