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essentially identical results because the former method also yields an experimentally determined C2H3 entropy (55.9 (±2.6) cal mol-1 K"1) which is virtually the same as the theoretical value (55.5 (±0.5) cal mol"1 K"1). Since the enthalpy of formation and entropy determinations are coupled, high accuracy in the determination of one of these thermochemical quantities is a strong indication that the other is also accurate. In our prior study of the CH3 + HC1 reaction, a similar kinetic analysis, one which coupled our measured CH3 + HC1 rate constants with those for the Cl + CH4 reaction reported by Dobis and Benson and others,28 we also obtained exactly the correct entropy for CH3 and a heat of formation which was within ±0.2 kcal mol"1 of the most accurate prior determinations.1Recent studies using neutral reactants and products have obtained very similar values for the heat of formation of the C2H3 radical. Parmar and Benson12 obtained a C2H3 heat of formation within 1 kcal mol"1 of our value, in spite of the fact that their values for k] are lower than ours by a factor of 4. Wodtke and Lee have observed the velocity distribution of DF(u=4) from the F + C2D4 -» DF + C2D3 reaction.32 Since this information is a very sensitive function of the energetics of the reaction, it was possible to use the results of their experiments to determine a C2H3 heat of formation. They report a value of 65.6 (±0.5) kcal mol"1.

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Photofragmentations, state interactions, and energetics of Rydberg and ion-pair states: Resonance enhanced multiphoton ionization via E and V (B) states of HCl and HBr J. Chem. Phys. 138, 044308 (2013); 10.1063/1.4776260 Two-dimensional resonance enhanced multiphoton ionization of H i Cl; i = 35, 37: State interactions, photofragmentations and energetics of high energy Rydberg states J. Chem. Phys. 134, 164302 (2011); 10.1063/1.3580876 Polarizationresolved (2+1) resonanceenhanced multiphoton ionization spectroscopy of CF3I (6s) Rydberg states J. Chem. Phys. 98, 4355 (1993); 10.1063/1.464997[3+2] resonance enhanced multiphoton ionization of I and Br formed from the infrared multiphoton decomposition of CF3I and CF3BrTime-of-flight mass spectrometry has been used to examine the spatial aniso.tropy and. . translational energy of 1+ and CFt fragments resulting from resonant multtphoton excttatIon of CF 31 in the 300-306 nm range. These ion species are shown to be largely the photofragments from the single-photon direct dissociation of CF 3 1+ generated via a new resonant (2 + 1) multi photon ionization (MPI) transition. ghotoelectron spectroscopy shows that most of the parent CF 3 1+ is produced in its ground X 2E3/2 state by the resonant MPI process .. All the observed 1+ is formed via this parent ion photodissociation, while the observed CFt IS formed via statistical decomposition of the parent as well as parent ion photodissociation. The present results are discussed in the context of the current understanding of alkyl halide photodynamics.

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