Photoelectron spectroscopy of Rydberg states of the methyl radical

Photoelectron spectra following two-photon resonant, three-photon ionization of CH3 and CD3 via selected vibronic levels of the 3p(z) and 4p(z) Rydberg states are reported. Because the 3p(z) and 4p(z) Rydberg orbitals are non-bonding, the geometries of the corresponding Rydberg states of CH3 and CD3 are similar to those of the ground states of CH3+ and CD3+, respectively. This results in nearly diagonal Franck-Condon factors, with the photoelectron spectra showing a strong propensity for the preservation of the vibrational state upon ionization. The results are compared with earlier studies of the photoelectron spectra of analogous Rydberg states of NH3. (C) 1999 Elsevier Science B.V. All rights reserved.