A study of the aminomethyl radical CH 2NH 2 by vacuum UV photoelectron spectroscopy and ab initio molecular orbital calculations

Abstract

Ultraviolet photoelectron spectra have been recorded for the reaction of atomic fluorine with methylamine at different reaction times. A band associated with a short-lived reaction product has been recorded with adiabatic and vertical ionization energies of 6.29 ± 0.03 and 6.97 ± 0.03 eV respectively. Two vibrational series with average separations of 1810 ± 50 and 1190 ± 50 cm −1 were observed in this band. Comparison between the experimental ionization energies and ionization energies computed for CH 2NH 2( X 2 A′) and CH 3NH( X 2 A″), in addition to inspection of computed vibrational frequencies of CH 2NH 2 + ( X 1 A 1) and CH 3NH + ( X 3 A″) led to assignment of the photoelectron band to the ionization process CH 2NH 2 + ( X 1 A 1) ← CH 2NH 2( X 2 A′). The larger vibrational series was assigned to excitation of the CN stretching mode in the ion while the smaller series was assigned to excitation of a CH 2 out-of-plane vibration. The experimental adiabatic ionization energy has been combined with the known heat of formation of CH 2NH 2( X 2 A′), to yield the heat of formation Δ H ⦵ f(298) of CH 2NH 2 + ( X 1 A 1) as 755 ± 11 kJ Mol −1.