title: Core level (S 2p) excitation and fragmentation of the dimethyl sulfide and dimethyldisulfide molecules.
abstract: Electronic excitation and ionic dissociation of dimethylsulfide (DMS) and dimethyldisulfide (DMDS) have been studied around the S 2p edge using synchrotron radiation and time-of-flight mass spectrometry techniques. Mass spectra were obtained for both molecules, below, on and above the well defined resonances observed in the S 2p photoabsorption spectrum and centered at approximately 166 eV photon energy. Ab initio IS-CASSCF calculations were performed for a better understanding of the photoabsorption spectra. Similar calculations were also performed for the H(2)S molecule, in order to establish a bench mark. For both molecules, a higher fragmentation degree is observed with increasing photon energy. In the DMDS case, selective fragmentation was observed in the formation of the [CH(n)S](+) ions at the first S 2p resonance (corresponding to excitation to a σ*SS state) and in the formation of the [S(2)](+) and [S](+) ions at the third S 2p resonance (corresponding to excitation to a σ*CS state). Previously unreported doubly charged ([S](2+), [CH(3)](2+)) are observed for DMS and DMDS.
authors.affiliation: Instituto de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária, Ilha do Fundão, 21949-900, Rio de Janeiro, RJ, Brazil.
authors.forename: R B
authors.initials: RB
authors.lastname: Bernini
authors.forename: L B G
authors.initials: LB
authors.lastname: da Silva
authors.forename: F N
authors.initials: FN
authors.lastname: Rodrigues
authors.forename: L H
authors.initials: LH
authors.lastname: Coutinho
authors.forename: A B
authors.initials: AB
authors.lastname: Rocha
authors.forename: G G B
authors.initials: GG
authors.lastname: de Souza
mesh_terms: D000042:Absorption; D004220:Disulfides / Q000737:chemistry*; D004583:Electrons; D013058:Mass Spectrometry; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D013440:Sulfides / Q000737:chemistry*
chemical_list: D004220:Disulfides; D013440:Sulfides; C021181:dimethyl disulfide; C004784:dimethyl sulfide