A new electron-photon coincidence method for the measurement of lifetimes in atoms and molecules

Abstract

A new method of measurement of atomic and molecular lifetimes is described, in which delayed coincidences are recorded between inelastically scattered electrons and the subsequent decay photons. The main advantage of this method is that sources of systematic error, such as cascading, spectral line blending, radiation trapping and collisional de-excitation, can often be eliminated. The method is described in detail, together with measurements on three helium states: 3 3D(13.4+or-0.5)ns, 4 3S(63.5+or-1.2)ns and 4 1S(75+or-5)ns.