Pulsed laser desorption near a jet orifice: Concentration profiles of entrained perylene vapor

Abstract

We have investigated the entrainment in a jet expansion of material vaporized with a laser pulse from a surface below but closely adjacent to the jet orifice. Jets of He and Ar were used as carriers, and perylene was the test substance. Its distribution in space and time far from the nozzle was measured by laser-induced fluorescence and one-dimensional imaging with an optical multichannel analyzer. The width of the perylene concentration profile was found to be much narrower than the width of the gas expansion, especially in He. This makes it possible to extract a useful portion of the entrained material through a skimmer. Depending on the values of experimental parameters, the center of the profile first appears above, on, or below the jet axis and then moves lower with time. Effects of several parameters on shape and time-dependent position of the profile were investigated. The results can be used to optimize the overlap of the concentration pulse with a skimmer or other probe. © 1988 Springer-Verlag.