Laser temporal-coherence effects on multiphoton ionization processes

A single-transverse-mode $Q$-switched Nd-glass laser, which can operate over a number of longitudinal modes variable from 1 to 100, has been used to investigate laser temporal-coherence effects on the 11-photon ionization of xenon atoms. When the laser pulse has an over-all bandwidth of 4 ${\mathrm{cm}}^{-1\mathrm{}}$, the number of ions formed is enhanced by ${10}^{6.9\pm 0.3}$ over that produced by a monomode laser pulse with the same average laser intensity. The observed enhancement in the number of ions due to the change in temporal coherence of the pulse is in good agreement with recent theoretical prediction.