KINETIC ENERGIES OF HISTIDINE CU+ COMPLEXES DESORBED BY MEV PARTICLE BOMBARDMENT/

reflector-based method was used on a time-of-flight mass spectrometer of axial symmetry to measure relative initial kinetic energies of ions emitted from histidine samples under Cf-252 fission fragment bombardm ent, Results on pure histidine were consistent with previous measureme nts by other groups, thus confirming the validity of the method on thi s apparatus. Results on histidine and copper sulfate mixtures showed t wo distinct families of metal-containing ions: (1) cluster ions, like (CuCN)Cu+, that have high average kinetic energies and (2) adducts of copper with histidine, MCu+, that have a wider kinetic energy distribu tion with a lower average value. This confirmed the hypothesis that MC u+ should be formed in the diffuse 'ultratrack' region where energy tr ansfer occurs through indirect processes, involving time, space and sp eed scattering, while (CuCN)Cu+ should rather be emitted from the more energetic 'infratrack' region. The same hypothesis permitted explanat ion of the variation of (CuCN)Cu+ and MCu+ relative intensities with h istidine/copper sulfate proportions. A diminution of the relative quan tity of copper sulfate diminished the probability for high energy proc esses to occur in the small 'infratrack' region, and MCu+ ions could t hus appear with larger relative intensities, (C) 1998 John Wiley & Son s, Ltd.