title: Difluorocarbene studied with threshold photoelectron spectroscopy (TPES): measurement of the first adiabatic ionization energy (AIE) of CF(2).
abstract: The first photoelectron band of difluorocarbene CF(2), has been studied by threshold photoelectron (TPE) spectroscopy. CF(2) was prepared by microwave discharge of a flowing mixture of hexafluoropropene, C(3)F(6), and argon. A vibrationally resolved band was observed in which at least twenty-two components were observed. In the first PE band of CF(2), the adiabatic ionization energy differs significantly from the vertical ionization energy because, for the ionization CF(2) (+) (X(2)A(1))+e(-) <-- CF(2) (X(1)A(1)), there is an increase in the FCF bond angle (by approximately 20 degrees ) and a decrease in the C--F bond length (by approximately 0.7 A). The adiabatic component was not observed in the experimental TPE spectrum. However, on comparing this spectrum with an ab initio/Franck-Condon simulation of this band, using results from high-level ab initio calculations, the structure associated with the vibrational components could be assigned. This led to alignment of the experimental TPE spectrum and the computed Franck-Condon envelope, and a determination of the first adiabatic ionization energy of CF(2) as (11.362+/-0.005) eV. From the assignment of the vibrational structure, values were obtained for the harmonic and fundamental frequencies of the symmetric stretching mode (nu(1)') and symmetric bending mode (nu(2)') in CF(2) (+) (X(2)A(1)).
authors.affiliation: School of Chemistry, University of Southampton, Highfield, UK.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Innocenti
authors.forename: Marie
authors.initials: M
authors.lastname: Eypper
authors.forename: Edmond P F
authors.initials: EP
authors.lastname: Lee
authors.forename: Stefano
authors.initials: S
authors.lastname: Stranges
authors.forename: Daniel K W
authors.initials: DK
authors.lastname: Mok
authors.forename: Foo-tim
authors.initials: FT
authors.lastname: Chau
authors.forename: George C
authors.initials: GC
authors.lastname: King
authors.forename: John M
authors.initials: JM
authors.lastname: Dyke
mesh_terms: D000465:Algorithms; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D011789:Quantum Theory; D013057:Spectrum Analysis / Q000379:methods; D013816:Thermodynamics; D014732:Vibration
chemical_list: D006845:Hydrocarbons, Fluorinated; C121084:difluorocarbene