Browsing by Author "Fang, Jing-Wen"

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Dynamics of the F(2) Reaction with Propene: The Effect of Methyl Substitution
(2009-04-23)
Fang, Jing-Wen
;
Xie, Tingxian
;
Chen, Hsueh-Ying
;
Lu, Yu-Ju
;
Lee, Yuan T.
The reaction of F(2) + C(3)H(6) has been investigated with the crossed molecular beam technique. The only observed primary product channel is F + C(3)H(6)F while the HF + C(3)H(5)F channel cannot be found. The reaction cross section was measured as a function of collision energy and the reaction threshold was determined to be 2.4 +/- 0.3 kcal/mol. Compared to the reaction threshold of the F(2) + C(2)H(4) reaction, the methyl substitution effectively reduces the reaction threshold by about 3 kcal/mol. The product time-of-flight spectra and angular distributions were measured and analyzed. The angular distribution displays strongly backward, indicating that the reaction is much faster than rotation. All experimental results support a rebound reaction mechanism, which agrees with the structure of the calculated transition state. The transition state geometry also suggests an early barrier; such dynamics is consistent with the observed small kinetic energy release of the products. Except for the different values of the reaction thresholds, the dynamics of the F(2) + C(2)H(4) and F(2) + C(3)H(6) reactions are remarkably similar.
Dynamics of the F(2) reaction with the simplest pi-bonding molecule
(2008-05-14)
Lu, Yu-Ju
;
Xie, Tingxian
;
Fang, Jing-Wen
;
Shao, Hua-Chieh
;
Lin, Jim J.
The reaction of F(2)+C(2)H(4) has been investigated with crossed molecular beam experiments and high level ab initio calculations. For a wide range of collision energies up to 11 kcal/mol, only one reaction channel could be observed in the gas phase. The primary products of this channel were identified as F+CH(2)CH(2)F. The experimental reaction threshold of collision energy was determined to be 5.5 +/- 0.5 kcal/mol. The product angular distribution was found to be strongly backward, indicating that the reaction time scale is substantially shorter than rotation. The calculated transition state structure suggests an early barrier; such dynamics is consistent with the small product kinetic energy release measured in the experiment. All experimental results consistently support a rebound reaction mechanism, which is suggested by the calculation of the intrinsic reaction coordinate. This work provides a clear and unambiguous description of the reaction dynamics, which may help to answer the question why the same reaction produces totally different products in the condensed phase. (C) 2008 American Institute of Physics.
Dynamics of the F-2 Reaction with Propene: The Effect of Methyl Substitution
(2009-04-23)
Fang, Jing-Wen
;
Xie, Tingxian
;
Chen, Hsueh-Ying
;
Lu, Yu-Ju
;
Lee, Yuan T.
The reaction of F-2 + C3H6 has been investigated with the crossed molecular beam technique. The only observed primary product channel is F + C3H6F while the HF + C3H5F channel cannot be found. The reaction cross section was measured as a function of collision energy and the reaction threshold was determined to be 2.4 +/- 0.3 kcal/mol. Compared to the reaction threshold of the F-2 + C2H4 reaction, the methyl substitution effectively reduces the reaction threshold by about 3 kcal/mol. The product time-of-flight spectra and angular distributions were measured and analyzed. The angular distribution displays strongly backward, indicating that the reaction is much faster than rotation. All experimental results support a rebound reaction mechanism, which agrees with the structure of the calculated transition state. The transition state geometry also suggests an early barrier; such dynamics is consistent with the observed small kinetic energy release of the products. Except for the different values of the reaction thresholds, the dynamics of the F-2 + C2H4 and F-2 + C3H6 reactions are remarkably similar.