State-resolved imaging of CO from propenal photodissociation: Signatures of concerted three-body dissociation

Abstract

Articles you may be interested inDissociation of internal energy-selected methyl bromide ion revealed from threshold photoelectron-photoion coincidence velocity imaging Monte Carlo simulation of nitrogen dissociation based on state-resolved cross sections Phys. Fluids 26, 012006 (2014); 10.1063/1.4862541Raman spectroscopy and crystal-field split rotational states of photoproducts CO and H2 after dissociation of formaldehyde in solid argon H and D release in 243.1 nm photolysis of vibrationally excited 3ν 1 , 4ν 1 , and 4ν CD overtones of propyne-d 3State-selected DC sliced images of propenal photodissociation show clear signatures of a novel synchronous concerted three-body dissociation of propenal recently proposed by Lee and co-workers to give C 2 H 2 + H 2 + CO [S. H. Lee, C. H. Chin, C. Chaudhuri, ChemPhysChem 12, 753 (2011)]. Unlike any prior example of a concerted 3-body dissociation event, this mechanism involves breaking three distinct bonds and yields 3 distinct molecules. DC sliced images of CO fragments were recorded for a range of rotational levels for both v = 0 and v = 1. The results show formation of two distinct CO product channels having dissimilar translational energy distributions with characteristic rovibrational state distributions. The images for CO (v = 0) show a large contribution of slower CO fragments at lower rotational levels (J = 5-25). This slow component is completely absent from the v = 1 CO images. The images for the higher rotational levels of the v = 0 and v = 1 CO are nearly identical, and this provides a basis for decomposing the two channels for v = 0. The quantum state and translational energy distributions for the slow channel are readily assigned to the 3-body dissociation based on the properties of the transition state. The faster CO fragments dominating the higher rotational levels in both v = 0 and v = 1 are attributed to formation of CH 3 CH + CO, also in agreement with the inferences based on previous non-state-resolved measurements with supporting theoretical calculations.

Experimental and Theoretical Studies on the Dynamics of the O(3P) + Propene Reaction: Primary Products, Branching Ratios, and Role of Intersystem Crossing

“…Noteworthy, propanal can undergo a three-body dissociation via TS16 to C 2 H 4 + H 2 + CO. This process, however, although predicted by RRKM calculations to be very important in the photodissociation at 193 and 157 nm, 65 to date has not been observed in the UV photodissociation of propanal (while it has been observed in the photodissociation of propenal 64,66 ).…”

An automated transition state search using classical trajectories initialized at multiple minima

“…The three-body dissociation was thoroughly studied by Lee in a separate experimental study, 73 as well as by Suits and co-workers. 74 The discrepancies found between the product branching ratios calculated theoretically at 148 kcal mol À1 (ref. 72) with those obtained in the photolysis of propenal at 193 nm, 73,75 led Lee and co-workers to suggest that the three major channels (found experimentally): C 3 H 3 O + H, C 2 H 3 + HCO and C 2 H 4 + CO occur on an excited potential energy surface.…”

Direct Observation of Ethylidene (CH3CH), the Elusive High-Energy Isomer of Ethylene

“…Although methylketene can be readily synthesized, it spontaneously dimerizes on a time scale of hours at −60 °C, rendering experiments requiring long data accumulation times quite difficult. This prompted our investigation of the photodissociation of propenal (CH 2 CHCHO, also known as acrolein), an isomer of methylketene, which has only been studied previously at higher excitation energies. − …”