Vacuum ultraviolet photoelectron spectroscopy of transient species. Part 18.—The cyclopropyl, isopropyl and n-propyl radicals
Bands associated with the first ionization energies of the cyclopropyl, n-propyl and isopropyl radicals have been studied using a multidetector photoelectron spectrometer. In each case vibrational fine structure was recorded which was assigned with the aid of ab initio molecular-orbital calculations and force-field calculations. For the cyclopropyl radical the adiabatic and vertical ionization energies were measured as 8.18 ± 0.03 and 8.86 ± 0.02 eV, respectively. Regular vibrational structure, with an average spacing of 1000 ± 70 cm–1, is assigned to excitation of the pyramidal bending mode at the α-C-H position in the cyclopropyl ion. In the n-propyl and isopropyl cases spectra which are an improvement over those previously available have been obtained, and in both cases vibrational structure attributable to excitation of CCC bending modes in the ion have been resolved in the first photoelectron bands.