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Action spectroscopy of gas-phase carboxylate anions by multiple photon IR electron detachment/attachment

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Abstract

We report on a form of gas-phase anion action spectroscopy based on infrared multiple photon electron detachment and subsequent capture of the free electrons by a neutral electron scavenger in a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. This method allows one to obtain background-free spectra of strongly bound anions, for which no dissociation channels are observed. The first gas-phase spectra of acetate and propionate are presented using SF6 as electron scavenger and a free electron laser as source of intense and tunable infrared radiation. To validate the method, we compare infrared spectra obtained through multiple photon electron detachment/attachment and multiple photon dissociation for the benzoate anion. In addition, different electron acceptors are used, comparing both associative and dissociative electron capture. The relative energies of dissociation (by CO, loss) and electron detachment are investigated for all three anions by DFT and CCSD(T) methods. DFT calculations are also employed to predict vibrational frequencies., which provide a good fit to the infrared spectra observed. The frequencies of the symmetric and antisymmetric carboxylate stretching modes for the aliphatic carboxylates are compared to those previously observed in condensed-phase IR spectra and to those reported for gas-phase benzoate, showing a strong influence of the environment and a slight substituent effect on the antisymmetric stretch.

Year of Publication
2009
Journal
Journal of Physical Chemistry A
Volume
113
Number
17
Number of Pages
4941-4946
Date Published
Apr
Type of Article
Article
ISBN Number
1089-5639
Accession Number
ISI:000265529800017
URL
PId
29743f0832eae9835eac3ebb48646e92
Alternate Journal
J. Phys. Chem. A
Journal Article
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