title: Vacuum ultraviolet photoionization mass spectrometric study of cyclohexene.
abstract: In this work, photoionization and dissociation of cyclohexene have been studied by means of coupling a reflectron time-of-flight mass spectrometer with the tunable vacuum ultraviolet (VUV) synchrotron radiation. The adiabatic ionization energy of cyclohexene as well as the appearance energies of its fragment ions C6 H9 (+) , C6 H7 (+) , C5 H7 (+) , C5 H5 (+) , C4 H6 (+) , C4 H5 (+) , C3 H5 (+) and C3 H3 (+) were derived from the onset of the photoionization efficiency (PIE) curves. The optimized structures for the transition states and intermediates on the ground state potential energy surfaces related to photodissociation of cyclohexene were characterized at the ωB97X-D/6-31+g(d,p) level. The coupled cluster method, CCSD(T)/cc-pVTZ, was employed to calculate the corresponding energies with the zero-point energy corrections by the ωB97X-D/6-31+g(d,p) approach. Combining experimental and theoretical results, possible formation pathways of the fragment ions were proposed and discussed in detail. The retro-Cope rearrangement was found to play a crucial role in the formation of C4 H6 (+) , C4 H5 (+) and C3 H5 (+) . Intramolecular hydrogen migrations were observed as dominant processes in most of the fragmentation pathways of cyclohexene. The present research provides a clear picture of the photoionization and dissociation processes of cyclohexene in the 8- to 15.5-eV photon energy region.
authors.affiliation: National Synchrotron Radiation Laboratory, School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, 230029, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Chemistry, Qian Nan Normal College for Nationalities, Duyun, 558000, Guizhou, China.
authors.forename: Maoqi
authors.initials: M
authors.lastname: Cao
authors.affiliation: National Synchrotron Radiation Laboratory, School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, 230029, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Wei
authors.affiliation: National Synchrotron Radiation Laboratory, School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, 230029, China.
authors.forename: Mengmeng
authors.initials: M
authors.lastname: Ding
authors.affiliation: National Synchrotron Radiation Laboratory, School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, 230029, China.
authors.forename: Xiaobin
authors.initials: X
authors.lastname: Shan
authors.affiliation: National Synchrotron Radiation Laboratory, School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, 230029, China.
authors.forename: Fuyi
authors.initials: F
authors.lastname: Liu
authors.affiliation: National Synchrotron Radiation Laboratory, School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, 230029, China.
authors.forename: Liusi
authors.initials: L
authors.lastname: Sheng
mesh_terms: D053138:Cyclohexenes / Q000032:analysis* / Q000737:chemistry*; D007477:Ions / Q000032:analysis / Q000737:chemistry; D013058:Mass Spectrometry; D008958:Models, Molecular; D013056:Spectrophotometry, Ultraviolet; D017356:Synchrotrons; D014618:Vacuum
chemical_list: D053138:Cyclohexenes; D007477:Ions; C052568:cyclohexene
keywords: cyclohexene; mass spectrometry; photodissociation; photoionization; synchrotron radiation