Radiolysis of alcohols at low temperatures. Part 3.—Spectrophotometric investigation of trapped electrons and other species formed by gamma-irradiation in glassy methanol

Abstract

The absorption spectrum of electrons trapped in a glassy methanol matrix was investigated and its parameters were determined. The changes of these parameters on optical bleaching and their kinetics were studied ; it followed that thc broad spectrum is an envelope of partial spectra corresponding to different kinds of trapped electrons and to their various quantum transitions. The parameters of the spectra are influenced by the presence of some solutes.On optical bleaching, the electrons are excited to higher levels from which they collapse to a molecule giving the CH30ion and simultaneously a hydrogen atom. In accordance with this mechanism, the change in the yields of trapped electrons and total hydrogen caused by the presence of electron scavengers correspond to each other. The efficiencies of electron scavcngers at 77 K parallel roughly those in liquids at room temperature.The absorption of the irradiated glassy methanol in the u.-v. is evidently due to CH20H radicals as deduced from the kinetics of their disappearance and their reaction with tetranitromethane.

Dissociative electron attachment to dimethyl ether in irradiated 3-methylpentane glass

“…This can be compared with the reaction of a photoexeited trapped electron in pure alcohol glasses with the alcohol molecules of the trapping site. 15 Fujii and Willard suggested the possibility of e~+ 2CH3CH2OH -* CH3CH2O-+ CH3-CHOH + H2 in• ethanol glass as one of the pathways of decay of the trapped electron,16 which may be interpreted as due to the dissociative electron attachment as interpreted here.…”

Very low temperature pulse radiolysis. Protiated and perdeuterated methanol glasses at 6 K

“…Other salient features of these spectra are as follows: (1) The maxima of the pulse radiolysis spectra at 6 K are slightly red shifted from the maxima of the spectra which result from y radiolysis at 4.2 K. (2) The former spectra are broader than the latter with most of the increase in width being on the low energy side of the absorption maximum. (3) Both this red shift and this increase in width is larger for CD3OD than for CH3OH.…”

“…The selected dissociation enthalpy of TiS(g), 421 ± 42 kJ/mol at 0 K and 427 ± 42 kJ/mol at 298 K, is more uncertain than that of the monosulfide of any other first-row transition element. The selected value was principally based on mass spectrometric measurements by Edwards, Franzen, and Gilíes2 (EFG), who gave a value of 425.9 ± 7.5 kJ/mol for AH°(298) for the dissociation of TiS(g), and was influenced by the value 458 ± 13 kJ/mol at 0 K reported by Smoes et al 3 Values of other thermodynamic properties of TiS(g) and of TiS(s), which also were based on the mass spectrometric results of EFG, are correspondingly uncertain. The total rate of mass loss via vaporization of TiS(s) was measured as a function of temperature by the target collection method by Franzen and Gilíes4 (FG).…”

Optical absorption spectra of a solvated and stabilized electron in aliphatic alcohols

“…As is evident from this figure, the Z D 3 structure not having resulted merely from apparatus inaccuracies. At a temperature of about 300 K, a number of maxima may be ascertained in the absorption spectrum, e.g., 590,620,675,715, and 890 nm.…”