Abstract

Ar⁺ double peaks were observed in the time-of-flight spectra resulting from tunnel ionization of a xenon-argon gas mixture by an intense 10.6 µ laser. Experimental and theoretical analysis indicate that the double peaks are related to space-charge effects. Coulomb expansion of the two-component ion bunch produced in the laser focal region results in the formation of an external shell of Ar⁺ ions (due to its larger charge/mass ratio), surrounding the core of Xe⁺ ions (smaller charge/mass ratio). Subsequent cutting of Ar shell on the aperture diaphragm of the TOF mass-spectrometer produces two packets separated in space which correspond to Ar⁺ double peak observed.

© 1993 Optical Society of America