PHOTOELECTRON-SPECTROSCOPY OF CH2N-

We have measured the negative ion photoelectron spectra of CH2N- and CD2N- and find the electron affinities: EA(CH2N) = 0.511 +/- 0.008 eV and EA(CD2N) = 0.498 +/- 0.011 eV. Franck-Condon simulations of these spectra are carried out and we estimate the CH2N- and CH2N geometry differences; we fit our spectra with the following [constrained] molecular structures: [GRAPHICS] We combine our EA(CH2N) with the results of previous gas phase ion studies to extract a number of thermochemical parameters (kcal/mol): D0(0)(CH2N-H) = 85 +/- 5, D0(0)(H-CHN) = 23 +/- 6, D0(0)(H2C = N) = 144 +/- 6, and the isomerization enthalpy of H2CN+ --> HCNH+ is DELTA-H(isom) (C2-upsilon --> C-infinity-upsilon) = - 51 +/- 7. Attempts to calculate the geometry and vibrational frequencies of the H2CN radical are disappointing. Unrestricted Hartree-Fock and second-order M-phi-ller-Plesset ab initio calculations in a 6-31 + + G** basis produce badly spin-contaminated wave functions which do not reproduce the experimental findings.