Medium effects on weakly-bound complexes: Xe-CN in solid rare gases

The absorption and infrared emission spectra of the Xe-CN complex in solid Ne, Ar, and Kr were investigated and compared with CN in pure rare gases. The C-N stretching vibration of the complex exhibits much larger medium shifts from matrix to matrix than the frequency of CN itself. Unlike free CN, the Α2Π - Χ2Σ+ transition of complexed CN exhibits extreme broadening and lacks discrete vibrational structure. The general implications of these results for studies of weakly-bound complexes in matrices are discussed

Generation of C6H4+ by laser vaporization of magnesium with o-C6H4F2 in argon carrier gas

A route to efficient generation of C6H4+, potentially the benzyne radical cation, is presented. Laser vaporization of Mg+. and supersonic expansion in helium doped with o-, m-, or p-C6H4F2 yields, among other ions, o-, m-, p-C6H4F2Mg+.. complexes, but no C6H4+.. Collision-induced dissociation experiments show that the o-C6H4F2Mg+. complex can be converted into C6H4+. in a mildly energetic collision, with a center-of-mass energy around 1-2 eV. These conditions can also be reached in the ion source when argon is used as a carrier gas. In this way, mass spectra containing the desired m/z 76 peak, i.e. C6H4+., are obtained. Copyright (C) 2004 John Wiley Sons, Ltd