Laser ionization mass spectrometry of (N_xO_y)_n clusters

摘要

Picosecond, non-resonant multiphoton ionization followed by mass spectrometry has been used to investigate molecular clusters of the general form (N_xO_y)_n~+. The observed cluster ion distributions exhibit several types of "magic numbers." For example, the odd-electron clusters (NO)_n~+ and (NO)_nNO_2~+ show an odd-even intensity alternation which is rationalized in terms of electron pairing considerations. As another example the (NO)_3~+(N_2O)_n species are much more intense (stable) than clusters containing two or four nitric oxide molecules. This form of "magnic" is considered to be structural in nature. Finally, the stoichiometric cluster NO~+(NO)_n(NO_2)_n or NO~+(N_2O_3)_n is observed and attributed to photochemical rearrangement during the ionization process. The oxidation of the latter species to form NO_2~+(N_2O_3)_n is observed when water is present in the cluster.