Excited state dynamics of NaF:Cu+

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Abstract
We have previously used one‐ and two‐photon spectroscopy to characterize the vibronic structures observed for NaF:Cu+ in the excited states of the d 9s configuration. We were able to resolve the zero‐phonon lines and a progression of the first three or four quanta of the t1u vibration (involving the off‐center motion of Cu+). In the present work we model the line positions and intensities with a mixed quadratic–quartic spherical potential. The spherical potential along with a perturbative treatment of the crystal field describes the members of the 1T2g state progression well. We also semiquantitatively treat the Jahn–Teller effect, operative in the 1Eg state only. The fits indicate the existence of a radial barrier in the potential for the off‐center motion of Cu+ in the 1T2g and the 1Eg states of approximate magnitude 1.9 and 73 cm−1, respectively. We also find that the Cu+ ion moves preferentially toward the fluorines rather than between them in the 1T2g state. The derived potential energy surfaces are discussed in terms of the dynamical mixing of the excited 4s and 4p orbitals of Cu+.