ATTACHMENT OF SLOW ELECTRONS OF OXYGEN MOLECULES

The attachment of electrons to O2 molecules to form stable O2- ions is discussed by supposing that the electron is first captured to form an unstable negative molecular ion in a compound state, which is later stabilized in a collision with another molecule. The rate of initial capture is described by a Breit-Wigner formula and the rate of formation of stable O2- ions obtained by multiplying by the probability that a stabilizing collision should occur before the ion re-emits its extra electron. The lifetime of the compound state, which would be difficult to calculate reliably, cancels out of the resulting expression. If one supposes all collisions of unstable ions to be stabilizing, one obtains an upper bound of the order of 10-30 cm5 sec-1 for the rate constant for the formation of stable O2-. The experimental value is of this order.