Excited state dynamics of NaF:Cu+

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 t_1u 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 ¹T_2g state progression well. We also semiquantitatively treat the Jahn–Teller effect, operative in the ¹E_g state only. The fits indicate the existence of a radial barrier in the potential for the off‐center motion of Cu⁺ in the ¹T_2g and the ¹E_g 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 ¹T_2g state. The derived potential energy surfaces are discussed in terms of the dynamical mixing of the excited 4s and 4p orbitals of Cu⁺.