Vacuum ultraviolet photoelectron spectroscopy of transient species

Abstract

The He(I) photoelectron spectrum of the NCO(X 2Π) radical, produced from the gas phase reaction of atomic fluorine with isocyanic acid, has been recorded. Of the thirteen ionic states accessible from the neutral molecule with He(I) radiation, seven have been observed and assigned using the results of ab initio ΔSCF calculations. Evidence is presented to show that the X 3Σ- NCO+ potential energy surface is significantly different from those for the a 1Δ and b 1Σ+ ionic states. The first adiabatic ionization potential of NCO is measured as (11·76±0·01) eV and this leads to an estimate of D 0(N-CO+) of (4·40±0·16) eV. From the observed spectra predictions are made of possible electronic transition energies in NCO+.