Fragmentation of Energy-Selected SF5CF3+ Probed by Threshold Photoelectron Photoion Coincidence Spectroscopy: Bond Dissociation Energy of SF5-CF3 and Its Atmospheric Implications

The interaction of SF\(_5\)CF\(_3\) with vacuum-UV radiation has been investigated by photon induced fluorescence spectroscopy. Total fluorescence yield and dispersed fluorescence spectra of SF\(_5\)CF\(_3\) were recorded in the 200-1000 nm fluorescence window. In all cases, the fluorescence spectra resemble those of CF\(_3\)X (X=H, F, Cl, and Br) molecules. At photon energies below 20 eV, the emission is attributed to the excited CF\(_3\) and CF\(_2\) fragments. The threshold for the CF\(_3\) emission is 10.2 ± 0.2 eV, giving an upper-limit estimate for the SF\(_5\)-CF\(_3\) bond dissociation energy of 3.9 ± 0.3 eV. The excitation functions of the CF3 and CF2 emissions were measured in the photon energy range 13.6 – 27.0 eV. The resonant structures observed in SF\(_5\)CF\(_3\) are attributed to electronic transitions from valence to Rydberg orbitals, following similar assignments in CF\(_3\)X molecules. The photoabsorption spectrum of SF\(_5\)CF\(_3\) shows features at the same energies, indicating a strong contribution from Rydberg excitations

Section: Discussionsupporting

confidence: 73%

VUV photon induced fluorescence study of SF₅CF₃

Ruíz

Kivimäki²,

Stankiewicz

et al. 2006

“…[40] Briefly, TPEPICO spectra at high time resolution are measured as a function of photon energy over the Franck-Condon region of the repulsive state of the parent cation. By determining <KE> T as a function of hν, a linear extrapolation can be performed to determine the photon energy at which <KE> T would be zero.…”

Section: Fixed-energy Tpepico Spectramentioning

confidence: 99%

“…This quantity is termed the dissociative ionisation energy of the molecule, from which the absolute enthalpy of formation of the fragment ion can be determined. We applied this technique to dissociation from the repulsive electronic ground states of CF 4 + (to CF 3 + + F), SF 6 + (to SF 5 + + F) and CF 3 SF 5 + (to CF 3 + + SF 5 ), [40] and …”

Section: Fixed-energy Tpepico Spectramentioning

confidence: 99%

Fragmentation of valence electronic states of CF₃–CH₂F⁺and CHF₂–CHF₂⁺in the range 12–25 eV

Zhou

Seccombe

Tuckett

2002

Self Cite

“…9 As found for SF 6 , SF 5 CF 3 is not broken down by UV photodissociation in the stratosphere. 10 This leads naturally to the question as to whether there are any other atmospheric loss mechanisms. A recent electron attachment study shows that the molecule will be destroyed in the regions of the ionosphere where free electrons exist.…”

Section: Introductionmentioning

confidence: 99%

A study of the gas phase reactions of various cations with two derivatives of SF6; SF5CF3 and SF5Cl

Atterbury

Critchley

Kennedy

et al. 2002

A selected ion flow tube apparatus was used to investigate the positive ion chemistry of two derivatives of SF 6 ; SF 5 CF 3 and SF 5 Cl. This represents the first investigation of the positive ion chemistry of SF 5 Cl, and much of the data on SF 5 CF 3 is being presented here for the first time. Rate coefficients and ion product branching ratios have been determined at room temperature (300 K) for reactions with the following twenty-two cations; with SF 5 Cl, all of which have rate coefficients significantly less than the capture mechanism value. Several distinct processes are observed among the large number of reactions studied, including dissociative charge transfer and various abstraction channels. Non-dissociative charge transfer is not observed, implying that any parent ions formed dissociate rapidly to the fragment ions and associated neutrals.