The 6d→5f fluorescence spectra of PaCl2-6 in a Cs2ZrCl6 crystal

Emission spectra from the parity-allowed electronic transitions between the lowest crystal field level of the 6d1 configuration to all the electronic levels of the 5f1 configuration of Pa4+ diluted into single crystals of Cs2ZrCl6 at 4.2 K show highly structured vibronic sidebands. Vibronic progressions are seen along the 310 cm-1 totally symmetric stretch of the PaCl2-6 complex. Most vibronic peaks correspond to even parity vibrations of the PaCl2-6 complex or the host lattice. Additionally, electronic Raman scattering was observed between the two lowest crystal field levels of the 5f1 configuration by exciting with an argon ion laser in near resonance with the lowest level of the 6d1 configuration