High Resolution Spectroscopy of Neutral Yb Atoms in a Solid Ne Matrix

Abstract

We present an experimental and theoretical study of the absorption and emission spectra of Yb atoms in a solid Ne matrix at a resolution of 0.025 nm. Five absorption bands were identified as due to transitions from the 4f 14 5d 0 6s 2 1 S0 ground state configuration to 4f 14 5d 0 6s6p and 4f 13 5d 1 6s 2 configurations. The two lowest energy bands were assigned to outer-shell transitions to 6s6p 3 P1 and 1 P1 atomic states and displayed the structure of a broad doublet and an asymmetric triplet, respectively. The remaining three higher-frequency bands were assigned to inner-shell transitions to distinct J = 1 states arising from the 4f 13 5d 1 6s 2 configuration and were highly structured with narrow linewidths. A classical simulation was performed to identify the stability and symmetry of possible trapping sites in the Ne crystal. It showed that the overarching 1+2 structure of the high frequency bands could be predominantly ascribed to crystal field splitting in the axial field of a 10atom vacancy of C4v symmetry. Their prominent substructures were shown to be manifestations of phonon sidebands associated with the zero-phonon lines on each crystal field state. Unprecedented for a metal-rare gas system, resolution of individual phonon states on an allowed electronic transition was possible under excitation spectroscopy which reflects the semi-quantum nature of solid Ne. In contrast to the absorption spectra, emission spectra produced by steady-state excitation into the 1 P1 absorption band consisted of simple, unstructured fluorescence bands.