Infrared laser multiple photon ionization

The production of ions as a result of the interaction of intense CO 2 laser pulses with a variety of organic molecules is reported. The laser frequency dependence of the ionization follows closely the linear infrared absorption spectrum of the respective molecule. The extent of ionization depends very strongly on laser energy fluence. The ion-production process is found to have a strongly collisional character. Various possible mechanisms of laser-induced ionization are discussed, and evidence is presented favoring laser-induced chemi-ionization. © 1980 American Institute of Physics.