Photoelectron spectroscopy of low valent organophosphorus compounds, P-CH 3 , H-PCH 2 and PCH 2 .

We report the mass-selected slow photoelectron spectra of three reactive organophosphorus species, PCH 2 , and the two isomers, methylenephosphine or phosphaethylene, HPCH 2 and methylphosphinidine, P-CH 3 . All spectra were recorded by double imaging photoelectron-photoion coincidence spectroscopy (i 2 PEPICO) using synchrotron radiation and all species were generated in a flow reactor by the reaction of trimethyl phosphine with fluorine atoms. Adiabatic ionisation energies of 8.80 ± 0.02 eV (PCH 2 ), 10.07 ± 0.03 eV (H-PCH 2 ) and 8.91 ± 0.04 eV (P-CH 3 ) were determined and the vibronic structure was simulated by calculating Franck-Condon factors from optimised structures based on quantum chemical methods. Observation of biradicalic P-CH 3 isomer with its triplet ground state is surprising because it is less stable than H-PCH 2 .