Simultaneous LIF and REMPI analysis of fragments after photolysis of vibrationally high excited CF2CFCl

Roßberg, M.; Wolbrandt, J.; Strube, W.; Linke, E.

doi:10.1016/0022-2860(95)08678-o

Cited by 4 publications

(3 citation statements)

References 6 publications

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“…The narrow band around 430 nm emerging on top of a much broader structure is attributed to the CH radical (A 2 Δ → X 2 Π). The CH B 2 Σ → X 2 Π transition around 389 nm is overshadowed by what could be the CFCl emission (A → X), as observed by Rossberg et al in the 350−450 nm region . It should be noted again that neither atomic emission lines nor continuum emission are observed in the spectrum (i.e., the strongest expected lines are C I at 247.86 nm, F I at 685.60 nm, Cl I at 837.59 nm, H I α at 656.20 nm).…”

Section: Resultsmentioning

confidence: 74%

“…The CH B 2 Σ f X 2 Π transition around 389 nm is overshadowed by what could be the CFCl emission (A f X), as observed by Rossberg et al in the 350-450 nm region. 46 It should be noted again that neither atomic emission lines nor continuum emission are observed in the spectrum (i.e., the strongest expected lines are C I at 247.86 nm, F I at 685.60 nm, Cl I at 837.59 nm, H I R at 656.20 nm). This is in contrast with typical results obtained from LIBS, where continuum emission followed by atomic emission dominates the spectrum.…”

Section: Resultsmentioning

confidence: 91%

“…45 These photochemical pathways result from the relatively high strength of the C-F bond (typically 485 kJ/mol as compared to, e.g., 350 kJ/mol for the C-C bond). Fragmentation of the parent molecule (or parent ion) 46 and of heavier fragments is certainly driven by weaker bonds, which leads in the end to the production of the stable radical CF 2 .…”

Section: Resultsmentioning

confidence: 99%

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Sensing of Halocarbons Using Femtosecond Laser-Induced Fluorescence

Luo

Boudreau

et al. 2004

Anal. Chem.

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A femtosecond laser-induced clean fluorescence technique was explored as a means to monitor halogenated alkanes in the atmosphere. Characteristic difluorocarbene radical (CF2) fluorescence in the UV-vis can be generated inside a femtosecond laser-induced filament for different halocarbons. We show that, due to different dissociation and excitation kinetics leading to fluorescence emission, it is possible to temporally resolve the characteristic fluorescence of CF2-containing halocarbons from that of background species, therefore enhancing the signal-to-noise ratio. Laboratory-scale experiments demonstrate the potential use of femtosecond laser-induced clean fluorescence for the remote sensing of halocarbons in the atmosphere. The combination of this detection strategy with LIDAR could allow the long-range monitoring of several atmospheric species with a single laser source, eventually leading to a better understanding of chemical and dynamic processes affecting global warming, ozone loss, tropospheric pollution, and weather prediction.

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Section: Resultsmentioning

confidence: 74%

Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

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Sensing of Halocarbons Using Femtosecond Laser-Induced Fluorescence

Luo

Boudreau

et al. 2004

Anal. Chem.

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Laser-Based Detection of Atmospheric Halocarbons

Gravel

Boudreau

Reviews in Fluorescence 2006

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Absolute Heats of Formation of CHCl, CHF, and CClF. A Gas-Phase Experimental and G2 Theoretical Study

1997

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The 298 K heats of formation of the singlet halocarbenes CHCl (1), CHF (2), and CClF (3) have been determined from measurements of the chloride dissociation energies of CHCl2 - (1a), CHClF- (2a), and CCl2F- (3a) and the gas-phase acidities of CH2Cl2 (1b), CH2ClF (2b) and CHCl2F (3b), respectively. Analysis of the energy-resolved collision-induced dissociation cross sections for 1a, 2a, and 3a obtained with a flowing afterglow−triple quadrupole instrument gives the 298 K chloride dissociation enthalpies: 37.0 ± 2.7, 22.7 ± 2.2, and 25.2 ± 1.5 kcal/mol, respectively. Proton transfer equilibrium and acid−base bracketing measurements carried out in the flow tube give gas-phase acidities, ΔH acid, for 1b, 2b, and 3b of 377.6 ± 0.7, 385.9 ± 0.3, and 361.3 ± 2.0 kcal/mol, respectively. The chloride dissociation enthalpies and gas-phase acidities are combined in simple thermochemical cycles to derive 298 K heats of formation for 1, 2, and 3 of 80.4 ± 2.8, 34.2 ± 3.0, and 7.4 ± 3.2 kcal/mol, respectively. Critical comparisons of these results with the results of prior experimental measurements and with the results of G2 molecular orbital calculations lead to the following recommended heats of formation (in kcal/mol): ΔH f,298(CHCl) = 78.0 ± 2.0, ΔH f,298(CHF) = 34.2 ± 3.0, ΔH f,298(CFCl) = 7.4 ± 3.2, ΔH f,298(CCl2) = 55.0 ± 2.0, and ΔH f,298(CF2) = −44.0 ± 2.0. The recommended heats of formation are used to derive other thermochemical data, including halocarbene proton affinities, PA(CXY), halomethyl radical acidities, ΔH acid(CHXY), and C−H bond strengths for halomethyl radicals, DH298(H−CXY). An excellent linear correlation is found to exist between the divalent state stabilization energy (DSSE) of the halocarbenes and the measured or calculated singlet−triplet splittings.

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Simultaneous LIF and REMPI analysis of fragments after photolysis of vibrationally high excited CF2CFCl

Cited by 4 publications

References 6 publications

Sensing of Halocarbons Using Femtosecond Laser-Induced Fluorescence

Sensing of Halocarbons Using Femtosecond Laser-Induced Fluorescence

Laser-Based Detection of Atmospheric Halocarbons

Absolute Heats of Formation of CHCl, CHF, and CClF. A Gas-Phase Experimental and G2 Theoretical Study

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