Photoelectron spectroscopy of the CH3N− ion

We have observed the negative ion photoelectron spectrum of the methylnitrene 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(X̃ 3A2), we also detect the first electronically excited state of methylnitrene, ã 1E. We measure the singlet/triplet splitting to be ΔE(ã 1E−X̃ 3A2)=1.352±0.011 eV. The photoelectron spectrum of CH3N ã 1E contains relatively sharp vibronic structure. Unlike the spectra from H2CC−, the photoelectron spectra for CH3N− show no evidence for a barrier separating the rearrangement of singlet methylnitrene to methyleneimine, [CH31N] → CH2=NH.