A crossed beam and ab initio study of the C2(X1Σg+ /a3∏u)+C2H2(X1Σg+) reactions

Experimental Investigation of Neutral-Neutral Reactions and Energy Transfer at Low Temperatures

“…Their ab initio calculations predict a barrierless potential energy surface, in good agreement with the high value of the rate constant at low temperatures. For 1 C 2 + C 2 H 2 , similar behavior is observed, and Kaiser et al (2003) found C 4 H + H products at 24.1 kJ mol −1 collision energy (2000 K). Remarkably, 1 C 2 also displays rapid rate constants with the saturated hydrocarbons CH 4 , C 2 H 6 and C 3 H 8 .…”

Chemical Dynamics of the Formation of the 1,3-Butadiynyl Radical (C4H(X2Σ+)) and Its Isotopomers

“…This structure could be accessed from the dicarbon and acetylene reactants either by addition of dicarbon to the carbon-carbon triple bond or via isomerization of s1 ( Figure 9). 1 However, this study could not determine if the forward-backward symmetry of this microchannel was the result of a lifetime of the diacetylene intermediate being longer than its rotational period or solely the consequence of the D ∞h symmetry of the "symmetric intermediate" (section 1). Also, the role of the s5 intermediate and its potential role in the molecular hydrogen elimination pathway remained to be resolved.…”

“…Our previous study suggested that up to three entrance channels could have been involved on the triplet C 4 H 2 surface; all pathways have no entrance barrier and proceed via addition of the dicarbon molecule to the carbon-carbon triple bond of the acetylene molecule forming t1, t2, and t3 ( Figure 9). 1 However, the relative contribution of these intermediates to the formation of the 1,3-butadiynyl radical product has not been resolved in the earlier study. It should be recalled that the derived centerof-mass angular distributions change from a forward-scattered shape to an enhanced intensity in the backward direction as the collision energy is increased.…”

“…However, our data clearly showed no sign of a molecular hydrogen loss, even at an enhanced signal-tonoise ratio of 20-30 compared to an earlier study of this reaction. 1 How can this apparent discrepancy be explained? In principle, the C 4 (a 1 Σ g + ) + H 2 (X 1 Σ g + ) products can be formed from the intermediates s3 and s5.…”

“…1 In recent years, this hydrogen-deficient molecule has received considerable attention due to its potential importance as a precursor to polycyclic aromatic hydrocarbons (PAHs) and possibly to fullerenes 2 in the interstellar medium, [3][4][5][6] in hydrocarbon-rich atmospheres of planets and their moons, 7,8 and in combustion processes. [9][10][11] The butadiynyl radical was first detected in 1975 in low-temperature argon and neon matrixes in its electronic ground state.…”