Browsing by Author "Pan, Jun-Wei"

Now showing 1 - 4 of 4

Barrierless reactions between two closed-shell molecules. I. Dynamics of F(2)+CH(3)SCH(3) reaction
(2008-03-14)
Lu, Yu-Ju
;
Lee, Lance
;
Pan, Jun-Wei
;
Xie, Tingxian
;
Witek, Henryk A.
A detailed experimental and theoretical investigation of the first-reported barrierless reaction between two closed-shell molecules [J. Chem. Phys. 127, 101101 (2007)] is presented. The translational energy and angular distributions of two product channels, HF+CH(2)SFCH(3) and F+CH(3)SFCH(3), determined at several collision energies, have been analyzed to reveal the dynamics of the studied reaction. Detailed analysis of the experimental and computational results supports the proposed reaction mechanism involving a short-lived F-F-S(CH(3))(2) intermediate, which can be formed without any activation energy. Other possible reaction mechanisms have been discriminated. The decay of the intermediate and competition between the two product channels have been discussed. (c) 2008 American Institute of Physics.
Barrierless reactions between two closed-shell molecules. II. Dynamics of F(2)+CH(3)SSCH(3) reaction
(2009-01-07)
Shao, Hua-Chieh
;
Xie, Tingxian
;
Lu, Yu-Ju
;
Chang, Chih-Hsuan
;
Pan, Jun-Wei
A second example of a barrierless reaction between two closed-shell molecules is reported. The reaction F(2)+CH(3)SSCH(3) has been investigated with crossed molecular beam experiments and ab initio calculations. Compared with previous results of the F(2)+CH(3)SCH(3) reaction [J. Chem. Phys. 127, 101101 (2007); J. Chem. Phys. 128, 104317 (2008)], a new product channel leading to CH(3)SF+CH(3)SF is observed to be predominant in the title reaction, whereas the anticipated HF+C(2)H(5)S(2)F channel is not found. In addition, the F+C(2)H(6)S(2)F product channel, the analog to the F+C(2)H(6)SF channel in the F(2)+CH(3)SCH(3) reaction, opens up at collision energies higher than 4.3 kcal/mol. Angular and translational energy distributions of the products are reported and collision energy dependences of the reaction cross section and product branching ratio are shown. The reaction barrier is found to be negligible (< 1 kcal/mol). Multireference ab initio calculations suggest a reaction mechanism involving a short-lived intermediate which can be formed without activation energy.
Barrierless reactions between two closed-shell molecules. II. Dynamics of F-2+CH3SSCH3 reaction
(2009-01-07)
Shao, Hua-Chieh
;
Xie, Tingxian
;
Lu, Yu-Ju
;
Chang, Chih-Hsuan
;
Pan, Jun-Wei
A second example of a barrierless reaction between two closed-shell molecules is reported. The reaction F-2+CH3SSCH3 has been investigated with crossed molecular beam experiments and ab initio calculations. Compared with previous results of the F-2+CH3SCH3 reaction [J. Chem. Phys. 127, 101101 (2007); J. Chem. Phys. 128, 104317 (2008)], a new product channel leading to CH3SF+CH3SF is observed to be predominant in the title reaction, whereas the anticipated HF+C2H5S2F channel is not found. In addition, the F+C2H6S2F product channel, the analog to the F+C2H6SF channel in the F-2+CH3SCH3 reaction, opens up at collision energies higher than 4.3 kcal/mol. Angular and translational energy distributions of the products are reported and collision energy dependences of the reaction cross section and product branching ratio are shown. The reaction barrier is found to be negligible (< 1 kcal/mol). Multireference ab initio calculations suggest a reaction mechanism involving a short-lived intermediate which can be formed without activation energy.
Dynamics of the F-2+CH3SCH3 reaction: A molecule-molecule reaction without entrance barrier
(2007-09-14)
Lu, Yu-Ju
;
Lee, Lance
;
Pan, Jun-Wei
;
Witek, Henryk A.
;
Lin, Jim J.
The F-2+CH3SCH3 reaction was studied with crossed molecular beam techniques and high level ab initio calculations. Significant reactivity was observed even at low collision energies, consistent with the negligible barrier height obtained from the ab initio calculations. All experimental findings are consistent with a weakly bound reaction intermediate of F-F-S(CH3)(2) structure, which possesses a special type of three-center four-electron bonding. Analogous intermediates can also explain the reactions of F-2 with CH3SH and CH3SSCH3.