Infrared spectroscopy and theory of the formaldehyde cation and its hydroxymethylene isomer.
Pulsed discharges in supersonic expansions containing the vapor of different precursors (formaldehyde, methanol) produce the m/z = 30 cations with formula [H2,C,O]+. The corresponding [H2,C,O]+Ar complexes are produced under similar conditions with argon added to the expansion gas. These ions are mass selected in a time-of-flight spectrometer and studied with infrared laser photodissociation spectroscopy. Spectra in the 2300-3000 cm-1region produce very different vibrational patterns for the ions made from different precursors. Computational studies with harmonic methods and various forms of anharmonic theory allow detailed assignment of these spectra to two isomeric species. Discharges containing formaldehyde produce primarily the corresponding formaldehyde radical cation, CH2O+, whereas those with methanol produce exclusively the cis- and trans-hydroxymethylene cations, HCOH+. The implications for the interstellar chemistry of these cations are discussed.
Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA.
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Mauney
Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA.
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Mosley
Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.
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Madison
Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.
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McCoy
Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA.
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Duncan