Infrared absorption and electron paramagnetic resonance studies of vinyl radical in noble-gas matrices

Abstract

Vinyl radicals produced by annealing-induced reaction of mobilized hydrogen atoms with acetylene molecules in solid noble-gas matrices (Ar, Kr, and Xe) were characterized by Fourier transform infrared and electron paramagnetic resonance (EPR) spectroscopies. The hydrogen atoms were generated from acetylene by UV photolysis or fast electron irradiation. Two vibrational modes of the vinyl radical (nu7 and nu5) were assigned in IR absorption studies. The assignment is based on data for various isotopic substitutions (D and 13C) and confirmed by comparison with the EPR measurements and density-functional theory calculations. The data on the nu7 mode is in agreement with previous experimental and theoretical results whereas the nu5 frequency agrees well with the computational data but conflicts with the gas-phase IR emission results.

Kinetics and mechanism of the radiation-chemical synthesis of krypton hydrides in solid krypton matrices

“…It is worth noting that the C 2 species (absorption at 1767 cm À 1 , Maier and Lautz, 1998), becomes "visible" in the IR spectrum only due to strong localized interaction with a xenon reducing its symmetry. On the other hand, no IR spectroscopic sign of C 2 was found in our work as well as in previous photochemical studies in argon or krypton matrices (Khriachtchev et al, 2003;Tanskanen et al, 2004;Tanskanen et al, 2005). This difference obviously means that C 2 remains IR-inactive in these matrices because of much weaker interaction with krypton and argon, which should be probably described as solvation rather than localized interaction.…”

“…It may imply both excitation transfer and positive hole transfer followed by the ion-electron recombination (more detailed consideration is given elsewhere : Feldman, 1999;Kobzarenko et al, 2012;Feldman, 2013). Anyway, according to the previous studies Tanskanen et al, 2005), the radiolysis of isolated acetylene molecules in a xenon matrix can be described by a two-step scheme Both С 2 Н radical and C 2 …Xe complex were observed in the IR spectra. It is worth noting that the C 2 species (absorption at 1767 cm À 1 , Maier and Lautz, 1998), becomes "visible" in the IR spectrum only due to strong localized interaction with a xenon reducing its symmetry.…”

Cryoradiolytic reduction of heme proteins: Maximizing dose-dependent yield

“…Cryogenic radiolysis of frozen solutions helps to avoid some of these difficulties because the diffusion of most of radiolysis products is severely limited in the glassy matrix (Willard 1975;Lin et al 1976;Kevan 1980). As a result cryogenic radiolysis in solid matrices provides *Corresponding author address: Stephen G. Sligar, University of Illinois Urbana-Champaign, 135 Morrill Hall, 505 S. Goodwin Avenue, Urbana, IL 61801, s-sligar@uiuc.edu, Phone: (217) Fax: (217) 265-4073.the possibility to accumulate trapped intermediates over extended periods of time, and to improve overall yield of the intermediate (Symons 1995;Feldman 1999;Tanskanen et al 2005).…”

Infrared spectrum of elusive C2F radical: A matrix-isolation and computational study

“…Importantly, the experimental bands of C 2 H (as well as HCCF) are much weaker than the photolysis-induced bands of C 2 F. This difference cannot be explained by a minor F + C 2 H channel because similarly small intensities of the C 2 H bands were observed in the photolysis of acetylene in solid matrices where the H + C 2 H photodissociation is the major channel [38,39]. This observation implies a large difference in the absorption cross-sections of C 2 F compared to C 2 H and HCCF, and this is exactly what is predicted by theory.…”