High-Resolution Spectroscopy of Some Transient Molecules
Abstract
High-resolution laser phosphorescence excitation spectra of various vibronic bands in the ~ a^3A_2>=ts ~ X^1A _1 system of rm H_2C ^{78}Se, H_2C^{80 }Se, and rm D_2C^ {80}Se have been observed with Doppler -limited resolution and eighteen bands have been rotationally analyzed. The ground state rotational constants of rm D_2C^{80}Se were improved by a simultaneous fitting of previously reported microwave data and combination differences from the 0 _sp{0}{0} and 4 _sp{0}{1} bands. The electronic transition has been shown to be singlet-triplet in nature by Zeeman effect studies, although much of the rotational structure can be analyzed as if it were due to a singlet-singlet transition. The excited state geometry was derived from the rotational analysis of the 0 _sp{0}{0} bands. A thorough analysis of the rotational structure of the 4_sp {0}{1} band of rm D_2C^{80}Se has shown that the energy level structure of the T_1 state of selenoformaldehyde corresponds to case (ab). A vibronically and partially rotationally resolved electronic spectrum of chlorofluorocarbene has been observed using the technique of pyrolysis jet spectroscopy. The rotational analysis of three bands established that the transition moment is perpendicular to the molecular plane and can be assigned as ~ A^1A ^{''}- ~ A^1A^'. The ground and excited state geometries were derived from the rotational analysis. The first high-resolution (0.002 cm^ {-1}) infrared spectrum of the nu_2 and nu_3 bands of formyl chloride have been obtained. The nu_3 type a/b hybrid band between 1220 and 1390 cm^{-1} has been rotationally analyzed, providing assignments for the a- and b-type lines of both HCO^ {35}Cl and HCO^{37 }Cl. The ground state rotational constants have been refined by a simultaneous fitting of previously reported microwave data and combination differences from the nu_3 and nu _6 bands of HCOCl. The excited state constants of both isotopomers have been obtained from fitting assignments over a wide range of J and K_{a} values. By comparing relative intensities, the ratio of the a-type to b-type transition moments was estimated to be 0.25 +/- 0.1. Extensive assignments of the rotational structure of the nu_2 bands of HCO ^{35}Cl and HCO^ {37}Cl have been made. Excited state perturbations have been found throughout the band, due to Delta K_{a}= 2 Fermi resonance and Delta K_{a }= 1 Coriolis interactions with the 3 ^15^1 vibrational state.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1994
- Bibcode:
- 1994PhDT........40J
- Keywords:
-
- FTIR;
- CHLOROFLUOROCARBENES;
- Chemistry: Physical; Physics: Molecular