Electron transmission spectroscopy is applied for the first time to a phospha-alkyne derivative, (CH3)(3)CCdropP. Electron attachment to the pi* LUMO in the gas-phase occurs at 0.63 eV. Formation of the temporary pi* anion state is also observed in measurements of the total anion current, as a function of the incident electron energy. Comparison with the ethyne analogue shows that replacement of a CH group with a P atom causes a very strong increase (2.3 eV) of the vertical electron affinity. Simple Koopmans' theorem calculations reproduce the experimental data. (C) 2002 Elsevier Science B.V. All rights reserved.