We recorded dispersed fluorescence (DF) spectra following excitation of the pure bending levels 20n and the combination states 101 20n and 20n 301 in the Ã A″1 ← X̃ A′1 system of HCF and DCF. Spectra were measured with a 0.3 m spectrograph equipped with a gated intensified charge coupled device (CCD) detector and obtained under jet-cooled conditions using a pulsed discharge source. The DF spectra reveal rich detail concerning the vibrational structure of the X̃ state up to 10 000 cm-1. For HCF, resonances among the nearly degenerate levels 11 2n, 2n+1 31, and 2n+2 produce a polyadlike structure in the spectrum, and the usual effective spectroscopic Hamiltonian (Dunham expansion) poorly reproduces the experimental term energies. In contrast, this Hamiltonian works well for the term energies of DCF. Density functional calculations of the ground state vibrational frequencies were performed; the results are in excellent agreement with the experimentally derived vibrational parameters. The search for perturbations involving the low-lying ã A″3 state is described.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry