1. Institute for Energy Problems of Chemical Physics, Russian Academy of Sciences, Leninsky Prosp. 38, bld.2, Moscow 119334, Russian Federation, N.N. Semenov's Institute of Chemical Physics, Russian Academy of Sciences, Kosygina 4, Moscow 119991, Russian Federation, and Biological and Medical Center, Laboratory for Biological and Medical Mass Spectrometry, Uppsala University, Box 583, S-75 123 Uppsala, Sweden