Dissociation of methanol and ethanol activated by a chemical reaction or by light

Abstract

When energized sufficiently either vibrationally or electronically, ROH (where R is methyl or ethyl) can dissociate to form H atoms and RO radicals. We have determined the translational energy release (〈ETr 〉=0.82Eavl ) and angular distribution (β=−0.60±0.03) from the laser induced fluorescence spectra of H atoms produced in the 193 nm photodissociation of CD3OH. We have also determined that the quantum yield for producing H from CD3OH is 0.86±0.10. In contrast, the reaction of O(1D)+CH4 which produces vibrationally excited CH3OH, has a quantum yield for producing H atoms of roughly 0.25 with only 22% of the available energy released as translation. We conclude that although the total available energy is the same in both cases, the dissociation of photoexcited methanol is prompt whereas the dissociation of chemically activated methanol shows some degree of internal vibrational equilibration.

A new method for atmospheric detection of the CH<sub>3</sub>O<sub>2</sub> radical

“…A photodissociation quantum yield of CH 3 O of 0.86 ± 0.10 has been found at 193.3 nm (Satyapal et al, 1989) in qualitative agreement with analysis of the end-products of the methanol photodissociation at 184.9 nm (Porter and Noyes, 1959;Buenker et al, 1984 Details on the HIRAC-based FAGE instrument for the detection of OH and HO 2 has been presented previously (Winiberg et al, 2015). Figure 1 shows a schematic cross section of the instrument inlet and the two fluorescence detection cells.…”

“…Although it is known, based on end-product analysis, that the scission of the O-H bond is a major photolysis channel of methanol at 184.9 nm (Buenker et al, 1984;Porter and Noyes, 1959), the photodissociation quantum yield of CH 3 O at 184.9 nm, CH 3 O, 184.9 nm , has not yet been reported. Here it is assumed that CH 3 O,184.9 nm is equal to the photodissociation quantum yield at 193.3 nm, CH 3 O, 193.3 nm = 0.86 ± 0.10, which has been reported (Satyapal et al, 1989 …”

“…The higher errors in C CH 3 O compared to C CH 3 O 2 are due to the uncertainty in the methanol concentration, which is not determined directly (vide supra), and the error in the yield of CH 3 O from CH 3 OH photolysis. The value of the CH 3 O photolysis yield from CH 3 OH reported at 193 nm was used (0.86 ± 0.10), which has an uncertainty of 12 % at the 1σ level (Satyapal et al, 1989).…”

Product pair correlation in CH3OH photodissociation at 157 nm: the OH + CH3channel

“…In photolysis of methanol at 193 nm, however, the dominant process is O-H bond rupture via the S 1 state. 14 In the photolysis of CD 3 OH at 193 nm, the ratio of H : D was determined to be 0.86 : 0.14; 82% of the total available energy was deposited into the translational degrees of freedom. Wen et al 15 detected H and D atoms from the photodissociation of three isotopic variants of methanol using the high-n Rydberg atom time-of-flight (HRTOF) technique.…”

Environmental effects of large igneous province magmatism: a Siberian perspective

“…They reported that the yield of H 2 was less than 25% of the yield of H from (b). Satyapal et al [1147] observed the production of H atoms in a pulsed laser experiment and reported a yield of H of (25±8)%. Matsumi et al [886] measured the yields of H and O( 3 P) in low pressure gas mixtures and reported that the yield of H was (15±3)% and the yield of O( 3 P) was <5%.…”