Collision-induced predissociation in the gas phase. Photolysis of methanol at 1849 Å

Abstract

The methanol photodecomposition quantum yield increases with the addition of different foreign gases (alkanes, rare gases, C 0 2 , SF6). Whereas the methanol absorption spectrum presents a continuum in the 1850 8, region, the added gas effect implies that collisions are involved in reaching the dissociative state. This apparent contradiction between photochemical and spectroscopic data leads to the postulate of the existence of a collision-induced predissociation. The efficiency of the different gases in promoting the predissociation correlates with their polarizability. In absence of spin-orbit coupling, the collision-induced predissociationc an be explained on the basis of a van der Wads interaction. With Kr and Xe as added gases, spin-orbit coupling is an additional dissociative channel.

Contributions From Grain Surface and Gas Phase Chemistry to the Formation of Methyl Formate and Its Structural Isomers

“…It is unclear from these results which set of branching ratios gives the best overall match to the relative abundances observed in Sgr B2(N). The set of branching ratios favoring the methoxy channel agrees qualitatively with gas phase laboratory measurements, which determined the overall branching fraction for the combined CH 3 O and CH 2 OH channels to be ∼0.75 (Hagege et al 1968). To our knowledge, no gas phase or condensed phase laboratory measurements have yet distinguished between these two channels through direct measurements of the products.…”

Photocoupling of Methane in Water Vapor to Saturated Hydrocarbons

“…So that OH radicals react with methyl radicals to produce methanol. However, we were not able to detect methanol in this work because as we have confirmed, UV irradiation (k = 185 nm) decomposes methanol through photodecomposition [23]. At high OH radical concentration, the methanol formed in the initial stage, undergoes further reaction with OH radicals to form oxygenated compounds such as formaldehyde (CH 2 O) and acetic acid (C 2 H 4 O 2 ), as reported by Ogura et al [9].…”

Direct Photolysis of 2-Propanol Vapor

“…In the first series, 11 Torr of 2-propanol was photolyzed in the presence of up to 1 atm of CO,. Carbon dioxide was chosen because Hagege et al (7) found that it was the most effective addend in increasing For personal use only. amount of CF, which has a small but finite study and the previously determined behavior vapor pressure at -196 "C. Again the rates of of this substrate and methanol in direct and formation of all products remain constant sensitized photolysis would indicate that the within experimental error or decline with the primary decomposition may proceed by two exce~tion of R(CH,COCH,).…”

“…Recently, Hagege et al (7) reported that in the direct photolysis of CH,OH at 1849 A, added inert gases increased the decomposition quantum yields. These workers suggested that this enhancement occurs through a collision induced predissociation.…”