H{sub 2} EJECTION FROM POLYCYCLIC AROMATIC HYDROCARBONS: INFRARED MULTIPHOTON DISSOCIATION STUDY OF PROTONATED ACENAPHTHENE AND 9,10-DIHYDROPHENANTHRENE

Journal Article · Thu Jan 20 00:00:00 EST 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/727/1/12· OSTI ID:21567622

Szczepanski, Jan; Vala, Martin T ^[1]; Oomens, Jos; Steill, Jeffrey D ^[2]

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1. Department of Chemistry and Center for Chemical Physics, P.O. Box 117200, University of Florida, Gainesville, FL 32611-7200 (United States)
2. FOM Institute for Plasma Physics 'Rijnhuizen', Edisonbaan 14, NL-3439MN Nieuwegein (Netherlands)

The infrared multiple-photon dissociation (IRMPD) spectra of protonated acenaphthene ([ACN+H]{sup +}) and 9,10-dihydrophenanthrene ([DHP+H]{sup +}) have been recorded using an infrared free electron laser after the compounds were protonated by electrospray ionization and trapped in a Fourier transform ion cyclotron mass spectrometer. In both compounds, the loss of two mass units is predominant. Density functional calculations (B3LYP/6-311++G(d,p)) of the infrared spectra of all possible protonated isomers of each species showed that the observed IRMPD spectra are best fit to the isomer with the largest proton affinity and lowest relative electronic energy. Potential energy surfaces of the most stable isomers of [ACN+H]{sup +} and [DHP+H]{sup +} have been calculated for H and H{sub 2} loss. The lowest energy barriers are for loss of H{sub 2}, with predicted energies 4.28 and 4.15 eV, respectively. After H{sub 2} ejection, the adjacent aliphatic hydrogens migrate to the bare ejection site and stabilize the remaining fragment. Single H loss may occur from [ACN+H]{sup +} but the energy required is higher. No single H loss is predicted from [DHP+H]{sup +}, only H migration around the carbon skeleton. The vibrational bands in the parent closed-shell protonated polycyclic aromatic hydrocarbons are compared to bands observed from the interstellar medium.

• OSTI ID: 21567622
• Journal Information: Astrophysical Journal, Vol. 727, Issue 1; Other Information: DOI: 10.1088/0004-637X/727/1/12; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ACENAPHTHENE
DENSITY FUNCTIONAL METHOD
DISSOCIATION
FOURIER TRANSFORMATION
FREE ELECTRON LASERS
HYDROGEN
INFRARED SPECTRA
LOSSES
MASS SPECTROMETERS
MULTI-PHOTON PROCESSES
PHENANTHRENE
PHOTONS
POLYCYCLIC AROMATIC HYDROCARBONS
VIBRATIONAL STATES
AROMATICS
BOSONS
CALCULATION METHODS
CONDENSED AROMATICS
ELEMENTARY PARTICLES
ELEMENTS
ENERGY LEVELS
EXCITED STATES
HYDROCARBONS
INTEGRAL TRANSFORMATIONS
LASERS
MASSLESS PARTICLES
MEASURING INSTRUMENTS
NONMETALS
ORGANIC COMPOUNDS
SPECTRA
SPECTROMETERS
TRANSFORMATIONS
VARIATIONAL METHODS