The yttrium dicarbide molecule, YC2, has been identified in the reactions of laser-ablated yttrium with methane and other small hydrocarbons under supersonic jet-cooled expansion conditions. A parallel-polarized electronic band system with origin at 12889.5 cm-1 has been tentatively identified as an A1 - X̃2A1 transition of a "T-shaped" isomer where the Y atom is bonded to the side of a C2 molecule. Weak vibronically induced perpendicular bands, representing Δv3=odd transitions, are also present. Extensive vibrational progressions in the excitation and the resolved fluorescence spectra have been analyzed to give the two lowest vibrational frequencies of the two electronic states: X̃2A1, v2 (a1) = 561.1(±2.8 cm-1), v3 (b2) = 369.6 (±1.7 cm-1); excited A1, v2=494.5(±5.0 cm-1), v3 = 331.6(±2.2 cm-1). No bands involving the C-C stretching vibration (v1,a1) have been found. The frequency of the v3 vibration in the ground state indicates that the barrier to internal rotation of the C2 group against the Y atom is quite high, but large anharmonic coupling between the v2 and v3 vibrations suggests that internal rotation is facilitated by excitation of the Y-C2 stretching vibration.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry