No abstract

The high-resolution He I photoelectron spectrum and the absolute vacuum-ultraviolet (vacuum-UV) absorption cross section (6-25 eV) as well as the ionic fragmentation of chlorine dioxide (OCIO) are reported. The photoelectron spectrum is interpreted in terms of exchange splitting effects of the various singlet and triplet cation states as well as by comparison to chemically related molecules. The vacuum-UV absorption spectrum shows different Rydberg series converging to the cation states. These Rydberg series and their vibrational progressions are assigned by term value arguments, dipole selection rules, and comparison with the photoelectron spectrum. Photoionization mass spectrometry is used for measurements of the ionization and fragmentation threshold of OCIO. The major fragment is C10+ which accurs above 13.4 eV. Thermochemical data such as heats of formation and bond dissociation energies are derived. No evidence for isomerization of OCIO+ is found, as observed for the electronically excited neutral molecule.

Using synchrotron radiation, the threshold photoelectron (TPES) spectrum of C 2 H 3 Cl and constant ion state (CIS) spectroscopy of C 2 H 3 Cl, are reported. For comparison, the He(I) photoelectron spectrum has also been measured and reexamined. The threshold photoelectron spectrum has been measured between 9.0 and 25.0 eV, and the photon energy range of 9.9-12.0 eV has been investigated in detail. Many features have been identified and tentatively assigned with the help of the photoabsorption spectroscopic results [1]. These data were compared with a well-resolved He(I) photoelectron spectrum. The fine structure observed in the two first ionic states is assigned to progressions belonging partially to previously unobserved vibration normal modes. State-selected CIS spectra have been recorded for the first vibronic states between 10.0 and 11.67 eV. They exhibit fine structure assigned to autoionization of Rydberg states.

No abstract

In this paper, we report the He(I) photoelectron spectrum (PES) and the threshold-photoelectron (TPES) spectrum of C 2 H 3 Br. The fine structure observed in the first two ionic states in the He(I) spectrum is assigned to progressions belonging partially to previously unobserved vibrational normal modes. The TPES has been measured between 9.0 and 25.0 eV, and the photon energy range of 9.8-12.0 eV has been investigated in more detail. Extensive calculations with the GAUSSIAN set of programs have been performed to help in the assignment of the observed features. Furthermore, a conical intersection between the à 2 A" and the 2 A" states was found to take place along the C-Br stretching coordinate. Intramolecular dynamics of the 2 A" state, initially prepared in the Frank-Condon region, was probed by the Fourier transform of the spectrum. The 2 A" state is almost readily depleted, most probably due to a very effective internal conversion through the conical intersection.