title: VUV and soft x-ray ionization of a plant volatile: Vanillin (C8H8O3).
abstract: Plant volatiles are emitted by plants in response to several forms of stress, including interaction with energetic photons. In the present work, we discuss the interaction of extreme UV and soft X-ray photons with a plant volatile, vanillin. The single and double (multiple) ionization of the vanillin molecule have been studied for the first time using time-of-flight mass spectrometry and VUV and soft X-ray photons (synchrotron radiation, at 12.0 eV, 21.2 eV, 130 eV, 310 eV, 531 eV, and 550 eV). At 12.0 and 21.2 eV, only singly charged species are observed and the parent ion, C8H8O3 (+), is the dominant species. Energy differences for some selected fragments were calculated theoretically in this energy region. At 130 eV, direct double and triple ionization of the valence electrons may occur. The fragmentation increases and CHO(+) becomes one of the main cations in the mass spectrum. The molecular ion is still the dominant species, but other fragments, such as C6H5O(+), begin to present similar intensities. At 310 eV, C 1s electrons may be ionized and Auger processes give rise to dissociative doubly ionized cations. Ionization around the O 1s edge has been studied both at the 531 eV resonance and above the ionization edge. Resonant and normal Auger processes play a significant role in each case and a large fragmentation of the molecule is observed at both photon energies, with intense fragments such as CHO(+) and CH3 (+) being clearly observed. A near edge X-ray absorption fine structure spectrum of the vanillin molecule was obtained around the O 1s ionization threshold. In addition, the fragmentation of vanillin has also been studied using a fast beam of electrons (800 eV), for the sake of comparison.
authors.affiliation: Instituto de Química, Universidade Federal do Rio de Janeiro (UFRJ) 21949-900 Rio de Janeiro-RJ, Brazil.
authors.forename: A Moreno
authors.initials: AM
authors.lastname: Betancourt
authors.affiliation: Instituto de Física, Universidade Federal do Rio de Janeiro (UFRJ) 21941-972 Rio de Janeiro-RJ, Brazil.
authors.forename: L H
authors.initials: LH
authors.lastname: Coutinho
authors.affiliation: Instituto Federal de Ciência e Tecnologia do Rio de Janeiro (IFRJ), 25050-100 Duque de Caxias-RJ, Brazil.
authors.forename: R B
authors.initials: RB
authors.lastname: Bernini
authors.affiliation: Instituto de Química, Universidade Federal do Rio de Janeiro (UFRJ) 21949-900 Rio de Janeiro-RJ, Brazil.
authors.forename: C E V
authors.initials: CE
authors.lastname: de Moura
authors.affiliation: Instituto de Química, Universidade Federal do Rio de Janeiro (UFRJ) 21949-900 Rio de Janeiro-RJ, Brazil.
authors.forename: A B
authors.initials: AB
authors.lastname: Rocha
authors.affiliation: Instituto de Química, Universidade Federal do Rio de Janeiro (UFRJ) 21949-900 Rio de Janeiro-RJ, Brazil.
authors.forename: G G B
authors.initials: GG
authors.lastname: de Souza
mesh_terms: D001547:Benzaldehydes / Q000737:chemistry / Q000528:radiation effects*; D013058:Mass Spectrometry; D008956:Models, Chemical; D017785:Photons; D013053:Spectrophotometry; D014466:Ultraviolet Rays; D055549:Volatile Organic Compounds / Q000737:chemistry / Q000528:radiation effects*; D014965:X-Rays
chemical_list: D001547:Benzaldehydes; D055549:Volatile Organic Compounds; C100058:vanillin