Communication: Photodissociation of CH3CHO at 308 nm: Observation of H-roaming, CH3-roaming, and transition state pathways together along the ground state surface

Abstract

The energy dependence of CO(v,J) produced from via the transition state, roaming, and triple fragmentation channels

Photoinduced C–H bond fission in prototypical organic molecules and radicals

“…Acetaldehyde and other aldehydes: Ion imaging and IR emission studies of the CO products formed when exciting CH3CHO at  > 300 nm imply pathways to forming CH4 + CO products involving both roaming H atoms and CH3 radicals. 106,107 Contributions from three different C-C bond fission mechanisms have also been identified as the photolysis wavelength is reduced across the range 328    265 nm, 108 while recent experiments (cavity ring down absorption measurements of product quantum yields 109 ) and theory (quasi-classical trajectory calculations 110 ) both provide evidence for some C-H bond fission, associated with triple fragmentation to H + CH3 + CO products, following excitation at  = 248 nm. H atom photoproducts have also been reported following excitation at  = 248 nm 111 and 205 nm.…”

H2 roaming chemistry and the formation of H3+ from organic molecules in strong laser fields

“…Typically, roaming takes place on a flat region of the potential energy surface, thus allowing nascent reaction products to remain near each other long enough for further reactions to occur. Of particular interest to the work presented, recent studies have focused on roaming processes in small organic molecules such as acetaldehyde 20 – 22 , acetone 23 , methyl formate 24 – 26 , and propane 27 . In most cases, the roaming pathway contributes a small fraction of the total yield.…”

Photodissociation of CF3CHO provides a new source of CHF3 (HFC-23) in the atmosphere: implications for new refrigerants.

“…The dissociation of CH 3 CHO via R2 has been reported to occur via up to three different dynamical channels. Although the interpretation of each channel is still not agreed upon in the literature [15][16][17], the key factor for this work is that all hypothesised channels yield CH 4 and CO as photoproducts following dynamics on S 0 after initial photo-excitation to S 1 . The two different CO dynamical signatures from CF 3 CHO dissociation in Fig.…”

“…However, following absorption of an ultraviolet photon, CH 3 CHO can also access a rich photochemistry on the ground electronic state (S 0 ). These many ground state photodissociation pathways are discussed in the following section and, most importantly, include the exoergic formation of methane (CH 4 ) and carbon monoxide (CO) [15][16][17]. Fluoroform (CHF 3 or HFC-23) is the product analogue of CH 4 for CF 3 CHO.…”