Calculations of the electron energy distribution function in mixtures of Se(1S), CO, and Xe are presented. The Se(1S) arises from photolysis of OCSe by Xe2vacuum ultraviolet excimer radiation, and the electrons are due to photoionization of the Se(1S). The calculations show that highly non‐Maxwellian electron energy distribution can result from electron heating by super‐elastic deexcitation of Se(1S) and cooling by inelastic excitation of CO vibrational levels and Xe electronic states. The kinetic rate constants computed using these distributions differ significantly from those derived from a Maxwellian distribution. It is found that the kinetic rate constants are sensitive to variations in the fractional ionization (&agr;≳10−6), relative CO concentration (nco/nSe(1S)⩾1), CO vibrational temperature (Tv≳1000 °K), and fractional Xe metastable density (n*/n≳ 10−5). Adding the molecular buffer, CO, cools electrons and slows multiplication.