Study of the mechanism of direct laser desorption/ionisation for some small organic molecules (M < 400 daltons)

Aspects of direct laser desorption/ionisation have been studied for three m olecules, aminotriazole (positive ion), dinoterb and ioxynil (negative ion) . The samples are deposited on metallic substrates, and a nitrogen laser is used for desorption/ionisation; ion yields are measured with a time-of-fli ght mass spectrometer, Previous work had shown that ion yields can strongly vary from one substrate to another, and that this variation does not refle ct the (calculated) metal surface temperatures. New results obtained in thi s work indicate that the desorption/ionisation mechanism is linked to the p hysical state of the substrate surface. Copyright (C) 1999 John Wiley & Son s, Ltd.