| Gas-phase reactions of iron ions, produced via a focused CO(,2) laser pulse on stainless steel, with several aromatic compounds have been characterized in a Fourier transform mass spectrometer (FTMS). In contrast to the electron impact spectra, those from the iron-ion reactions are diagnostic for isomers of many disubstituted benzene derivatives. The compounds studied were the ortho, meta, and para isomers of: xylene, methylanisole, fluoroanisole, bromoanisole, fluorotoluene, chlorotoluene, fluorobenzaldehyde, fluoronitrobenzene, bromofluorobenzene and chlorofluorobenzene. Only in the case of xylenes could none of the isomers be identified through these reactions.; The reactions of iron ions with several benzene and pentafluorobenzene derivatives were also studied, including halobenzenes. The Fe('+) induced dehydrohalogenation to form Fe(C(,6)H(,4))(,n)('+). Clusters for n = 1-6 were observed for chlorobenzene and bromobenzene, but clusters larger than n > 2 were not observed for fluorobenzene. Direct evidence of metal-catalyzed polymerization is observed in formation of (C(,6)H(,4))(,n)('+). Additional reaction channels were observed, but iodobenzene reactions were found to be different.; The effects of varying laser power and trap voltages were briefly investigated. Xylene showed increased intensity of the molecular ion (m/z 106) and m/z 91 (C(,7)H(,7)('+)) at higher laser power. Increasing the trap voltages in steps up to, but not beyond 2 V results in increased absolute ion intensity without altering the reaction mechanisms in the case of nitrobenzene.; Laser desorption of ions from condensed samples on a cooled metal support showed that no ions could generally be detected from the first few pulses, but molecular ion predominance is observed for subsequent laser pulses. Evidence of metal-ion reactions were also noted. No wavelength dependence on ion intensities was found, suggesting that multiphoton processes are not at work.; Construction and testing of a Seguin-type TEA-CO(,2) laser producing up to 15 J per pulse is also reported. The laser was coupled to a Varian CH/7 mass spectrometer. The system was computer interfaced to provide laser desorption information from the CH/7 probe tip. |
