MOLECULAR FRAGMENTATION AND FORMATION PROCESSES IN PLASMA DESORPTION MASS-SPECTROMETRY

Molecular fragmentation and formation processes in PDMS are studied by measuring and discussing positive and negative ion spectra of pure ca rbon or hydrocarbon compounds. Calculations of the hydrodynamic adiaba tic expansion of the material from the inner track result in the forma tion of carbon clusters in agreement with the negative ion spectra. A universal pattern in the negative ion spectra can thus be explained. R esults of molecular breakup calculations are compared with the observe d positive ions which are assumed to be from the ultratrack. From the comparison we conclude that the breakup of the carbon bonds is entropi c and takes place during the desorption while the main part of the hyd rogen separation occurs afterwards.