An electron impact ionization slit-jet apparatus for laser absorption spectroscopy Original Research Article

A continuous flow slit nozzle employing electron impact ionization for production of jet cooled ions and ionic clusters is described. The characteristics of the free-jet plasma have been probed using a quadrupole mass spectrometer system and by recording the rotational structure of the (2,0) vibrational band of the A 2φu−X2∑+g transition of N2+ via direct laser absorption. The rotational temperature of N2+ ions in the expanding plasma has been determined to be 28 K in the low J and 150 K in the high J limits. The slit-jet source is capable of producing useful quantities of cold cluster ions.