Raman Spectrum of Mass-Selected Terbium Dimers in Argon Matrixes

Abstract

We report on the absorption, resonance Raman, and Raman excitation profile spectra of mass-selected terbium dimers in argon matrixes. An absorption band found between 620 and 680 nm was assigned to terbium dimers. The Raman excitation profile of dimer frequencies resembles closely this absorption spectrum. Unlike other lanthanide dimers, resonance Raman spectra of terbium dimer, obtained by excitation into this region with tunable dye laser radiation, gives two progressions with one up to 7 Stokes transitions, and the other up to 4 transitions. We interpret these to represent two distinct electronic states X and A. For the ground (X) state, we obtain ωe = 137.6 ± 0.4 cm-1 with ωexe = 0.31 ± 0.05 cm-1, leading to a spectroscopic dissociation energy of 1.9 ± 0.3 eV, force constant ke = 0.88 ± 0.01 mdyn/Å. The first electronic (A) state has an origin at 313.9 cm-1 with a progression in ωe = 136.3 ± 0.2 cm-1 and ωexe = 0.14 ± 0.05 cm-1, leading to an excited-state spectroscopic dissociation energy of 4.1 ± 1.2 eV.