Photoelectron spectra of the nitrosomethane, trifluoronitrosomethane, nitrosyl fluoride, and nitrosyl chloride

He(I) p.e. spectra, qualitative m.o. models, and semiempirical calculations are presented for the title compounds to elucidate their electronic structures. No basic differences in the bonding of these isoelectronic and isostructural molecules have been found. Changes of ionization potentials within the series are attributed to differing hyperconjugative interactions of the substituents X and NO, and the electronegativities of X. During ionization experiments the temperature-dependent decomposition of dimeric cis-nitrosomethans into its monomers can be observed directly.