A simple laser vaporization source for thermally fragile molecules coupledto a supersonic expansion: application to the spectroscopy of tryptophan

The mass resolved electronic spectrum of cold tryptophan molecules has been obtained using a novel desorption method as a vaporization source coupled with a supersonic expansion. This desorption device is characterized by its simplicity, stability suitable for spectroscopic studies and by a very low yield of fragmentation products. The unique performance of the desorption source is demonstrated by the possibility to measure hole-burning spectra o f tryptophan by resonance enhanced two-photon ionization which confirms str ongly the presence of only a small number of stable conformers for this spe cies in its ground state. (C) 2000 Published by Elsevier Science B.V. All r ights reserved.