Fragment-free mass spectrometric analysis with jet cooling VUV photoionisation

We show that it is possible to obtain fragment-free mass spectra of large m olecules by a combination of laser desorption, jet cooling, and VUV single- photon photoionization. The ability to obtain parent molecular masses is pa rticularly important for the analysis of mixtures, such as combinations of fully saturated hydrocarbons. By varying the cooling conditions, we can als o achieve partial fragmentation in order to obtain further structural infor mation. The use of different wavelengths provides additional selectivity be tween aromatic and aliphatic compounds.