Exploring the Dynamics of Reaction C(³P) + C₂H₄ with Crossed Beam/Photoionization Experiments and Quantum Chemical Calculations

Abstract

We investigated the title reaction at collision energy 3.5 kcal mol(-1) in a crossed molecular beam apparatus using undulator radiation as an ionization source. Time-of-flight (TOF) spectra of product C(3)H(3) were measured in laboratory angles from 20° to 100° using two photoionization energies 9.5 and 11.6 eV. These two sets of experimental data exhibit almost the same TOF distributions and laboratory angular distributions. From the best simulation, seven angle-specific kinetic-energy distributions and a nearly isotropic angular distribution are derived for product channel C(3)H(3) + H that has an average kinetic-energy release of 15.5 kcal mol(-1), corresponding to an average internal energy of 33.3 kcal mol(-1) in C(3)H(3). Furthermore, TOF spectra of product C(3)H(3) were measured at laboratory angle 52° with ionizing photon energies from 7 to 12 eV. The appearance of TOF spectra remains almost the same, indicating that a species exclusively contributes to product C(3)H(3); the species is identified as H(2)CCCH (propargyl) based on the ionization energy of 8.6 ± 0.2 eV and the maximal kinetic-energy release of 49 kcal mol(-1). Theoretical calculations indicate that the rapid inversion mechanism and rotation in intermediate H(2)CCCH(2) can result in a forward-backward symmetric angular distribution for product C(3)H(3) + H. The present work avoids the interference of reactions of C((1)D) and C(2) radicals with C(2)H(4) and rules out the probability of production of other isomers like c-C(3)H(3) and H(3)CCC proposed in the previous work at least at the investigated collision energy.

Exploring the dynamics of C/H and C/Cl exchanges in the C(3P) + C2H3Cl reaction

“…11,12 A crossed molecularbeam apparatus equipped with an electron-impact or photon ionizer typically served to measure translational-energy distributions and angular distributions of products from an elementary reaction like C( 3 P) + C 2 H 4 → C 3 H 3 + H. [13][14][15] Kaiser et al 13 proposed two microchannels for the production of H 2 CCCH + H from the C( 3 P) + C 2 H 4 reaction at collision energies (E c ) 4.1 kcal mol −1 and 9.2 kcal mol −1 . In addition to the H 2 CCCH + H channel, Geppert et al 14 proposed the production of c-C 3 H 3 /CCCH 3 + H especially for the reaction with collision energy higher than 4 kcal mol −1 .…”

“…Chin et al 15 reinvestigated the reaction using synchrotron vacuum-ultraviolet (VUV) ionization to avoid interference of dissociative ionization of C 4 H 3 produced from reaction C 2 + C 2 H 4 → C 4 H 3 + H. 16 The selective VUV ionization merits much smaller (or negligible) dissociative ionization compared with conventional electron-impact ionization. 17, 18 Chin et al 15 indicated that propargyl (H 2 CCCH) radicals are exclusively produced with an isotropic angular distribution at E c = 3.5 kcal mol −1 .…”

“…17, 18 Chin et al 15 indicated that propargyl (H 2 CCCH) radicals are exclusively produced with an isotropic angular distribution at E c = 3.5 kcal mol −1 . A long-lived reaction complex can scatter products equivalently into the forward and backward hemispheres by rotation of the reaction system.…”

Dynamics of carbon-hydrogen and carbon-methyl exchanges in the collision of 3P atomic carbon with propene

“…Dynamics of the reaction C( 3 P) + C 2 H 4 → C 3 H 3 + H was investigated in crossed beams with time-offlight mass spectroscopy and electron-impact ionization or photoionization. [13][14][15][16] Product translational-energy distributions and angular distributions of the C 3 H 3 + H channel were measured via the detection of C 3 H 3 or H. Species C( 1 D) and C 2 are more or less producible in the generation process of atomic carbon so that reactions of C( 1 D) and C 2 with ethene need be taken care. Recently, the C( 3 P) + C 2 H 4 reaction was investigated at reactant collision energy (E c ) 3.5 kcal mol −1 in a crossed molecular-beam apparatus using synchrotron vacuum-ultraviolet (VUV) ionization.…”

“…Recently, the C( 3 P) + C 2 H 4 reaction was investigated at reactant collision energy (E c ) 3.5 kcal mol −1 in a crossed molecular-beam apparatus using synchrotron vacuum-ultraviolet (VUV) ionization. 16 Carbon atoms were produced from a mixture of 10% CO/He by pulsed discharge with a duration of 10 μs; the yield of C( 1 D) atoms was negligibly small due mainly to the quenching by CO. Furthermore, the selective (or soft) photoionization avoided the dissociative ionization of C 4 H 3 , produced from the reaction of C 2 radicals with ethene, to C 3 H 3 + + C. The C 3 H 3 product had a nearly isotropic angular distribution and was identified as the propargyl (H 2 CCCH) radical at E c = 3.5 kcal mol −1 .…”