Above-threshold ionisation

Abstract

Above-threshold ionisation (ATI) is the name given to the absorption of photons by an already ionised atomic electron. This is a new unexpected phenomenon in multi-photon physics. ATI has been found to occur readily at light intensities above 1 TW cm-2 in light pulses short enough to eliminate the influence of collisions. ATI arises from the simultaneous phase-coherent interaction of a single atomic electron with its parent ion and with laser light.