To further investigate the Renner-Teller (RT) effect and spin-orbit mixing in the Ã 1A″ ← X̃ 1A′ system of the simplest singlet carbene, HCF, we report a detailed analysis of the K a= 1 ← subband of 20 using polarization quantum beat spectroscopy in combination with fluorescence excitation spectroscopy and lifetime measurements. This subband is perturbed both by RT and spin-orbit interactions, which are clearly differentiated due to the order-of-magnitude difference in matrix elements. We show that RT induced mixing with a high vibrational level of X̃ 1 A′ leads to a splitting of this subband, and while the higher energy member is rotationally unperturbed, every line in the lower energy member is perturbed by spin-orbit mixing with background levels of ã 3A″, as evidenced by large 19F and 1H hyperfine constants and Lande g factors. In contrast, the higher energy subband exhibits very small Lande g factors and hyperfine constants, which is explained within a model that incorporates only the Ã 1A″-X̃ 1A′ interaction. We thus demonstrate that polarization quantum beat spectra provides efficient discrimination between RT and spin-orbit interactions. Analysis of the lower energy subband in concert with ab initio electronic structure calculations has yielded the first information on the 19F and 1H hyperfine structure of the ã 3A″ state and the magnitude of the spin-orbit matrix elements.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry