Nonradiative relaxation rates in CaF₂:Sm²⁺ measured by photoionization spectral holeburning

The temperature dependence of the width of spectral holes burned in the 4f6A1g→4f55d A1u absorption line (6958 Å) of CaF2+ has been measured and used to determine the phonon coupling which controls nonradiative relaxation between the A1u and Eu levels. We confirm an assertion made by Akimov and Kaplyanskii that the phonon coupling among the lowest three 4f55d levels of CaF2+ exhibits strong selection rules. In particular, the "deformational" Eg phonons are two orders of magnitude more effective than "rotational" T1g phonons in inducing nonradiative relaxation. © 1986.