Photoelectron spectroscopy of the CH3N- ion

We have observed the negative ion photoelectron spectrum of the methylnitre ne ion, CH3N-, and measured the electron affinity of methylnitrene, EA(CH3N ) = 0.022 +/- 0.009 eV. In addition to detaching the methylnitrene anion to the ground state of CH3N((X) over tilde (3)A(2)), we also detect the first electronically excited state of methylnitrene, (a) over tilde E-1. We meas ure the singlet/triplet splitting to be Delta E((a) over tilde E-1-(X) over tilde (3)A(2)) = 1.352 +/- 0.011 eV. The photoelectron spectrum of CH3N (a ) over tilde E-1 contains relatively sharp vibronic structure. Unlike the s pectra from H2CC-, the photoelectron spectra for CH3N- show no evidence for a barrier separating the rearrangement of singlet methylnitrene to methyle neimine, (1)[CH3N] --> CH2=NH. (C) 1999 American Institute of Physics. [S00 21-9606(99)00336-0].