Vibrational fluorescence from CN−defects in 12 alkali halide hosts, pumped intracavity withFBcolor-center laser

Vibrational emission (around 4.8 μm) of C${\mathrm{N}}^{-}$ defects was detected and studied at 80 K in 12 different alkali halide hosts. By pumping the weak C${\mathrm{N}}^{-}$ overtone absorption (at ∼ 2.4 μm) intracavity in a tunable $F_B\left(\mathrm{II}\right)$ center laser, excitation spectra, relative intensities, and lifetime values of the vibrational emission were measured in all hosts. Variation in the C${\mathrm{N}}^{-}$ defect concentration showed the existence of strong nonradiative luminescence quenching processes at C${\mathrm{N}}^{-}$ concentrations above ∼0.5%. This is interpreted to be due to intermolecular transfer and migration of the excitation energy to a "sink" with an efficient nonradiative decay channel. The pronounced observed effect of host material variation on the luminescence lifetime and intensity are discussed in terms of multiphonon or rotational models for relaxation processes, competing with the vibrational luminescence.