title: Measurement of ionic resonances in alkyl phenyl ketone cations via infrared strong field mass spectrometry.
abstract: Strong-field excitation of alkyl phenyl ketone molecules reveals an electronic resonance at 1370 nm in the radical cations upon measuring mass spectra as a function of excitation wavelength from 1240 to 1550 nm. The ratio of the benzoyl fragment ion to parent ion signal in acetophenone increases from 1:1.5 at 1240 nm excitation to 5:1 at 1370 nm (0.9 eV), and back to 1:1 at 1450 nm. Unlike acetophenone and propiophenone, the homologous molecules acetone and ethylbenzene exhibit no wavelength-dependent fragmentation patterns over the range from 1240 to 1550 nm, supporting the hypothesis that the electronic structure of the alkyl phenyl ketone cation enables the one-photon transition. Calculations on the acetophenone and propiophenone radical cations show the existence of a bright state, D2, 0.87 and 0.88 eV, respectively, above the ground-state D0 minimum. Calculations of the potential energy surfaces of the acetophenone radical cation suggest that a D2 → D0 radiationless transition precedes dissociation on D0. Upon population transfer to the D2 surface, the wavepacket motion is directed toward a three-state conical intersection (D0/D1/D2) that facilitates the photodissociation by converting electronic to vibrational energy on the D0 surface.
authors.affiliation: Center for Advanced Photonics Research, ‡Department of Chemistry, and §Department of Physics, Temple University , Philadelphia, Pennsylvania 19122, United States.
authors.forename: Timothy
authors.initials: T
authors.lastname: Bohinski
authors.forename: Katharine
authors.initials: K
authors.lastname: Moore Tibbetts
authors.forename: Maryam
authors.initials: M
authors.lastname: Tarazkar
authors.forename: Dmitri
authors.initials: D
authors.lastname: Romanov
authors.forename: Spiridoula
authors.initials: S
authors.lastname: Matsika
authors.forename: Robert
authors.initials: R
authors.lastname: Levis
mesh_terms: D002412:Cations / Q000737:chemistry; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry; D007659:Ketones / Q000737:chemistry*; D013058:Mass Spectrometry; D015394:Molecular Structure
chemical_list: D002412:Cations; D005609:Free Radicals; D007659:Ketones