Long-Delayed Fluorescence of Nd3+ in Pure LaCl3 and in LaCl3 Containing Ce3+

Abstract

Fluoresence from the ${}_{}{}^4{}_{}{}^{}F_{\frac{3}{2}}^{}{}_{}{}^{}$ level of ${\mathrm{Nd}}^{3+}$ in pure La${\mathrm{Cl}}_3$ and in La${\mathrm{Cl}}_3$ containing ${\mathrm{Ce}}^{3+}$ was found to be delayed appreciably (∼100 μsec) when levels above the ${}_{}{}^4{}_{}{}^{}F_{\frac{3}{2}}^{}{}_{}{}^{}$ level were selectively pumped with a pulse of light. Increasing the concentration of ${\mathrm{Nd}}^{3+}$ in La${\mathrm{Cl}}_3$ resulted in decreased delays; other evidence also suggests that cross relaxation between ${\mathrm{Nd}}^{3+}$ ions decreases the delay with increased concentration. Decreased delays in the ${\mathrm{Nd}}^{3+}$ fluorescence were obtained when the ${\mathrm{Ce}}^{3+}$ concentration was increased with the ${\mathrm{Nd}}^{3+}$ concentration fixed at 1%; however, when ${\mathrm{Ce}}^{3+}$ completely replaced the ${\mathrm{La}}^{3+}$, the neodymium surprisingly exhibited long fluorescent delays and lifetimes. Delays and lifetimes of higher lying levels for two crystals were examined at 4.2°K, 77°K, and room temperature.