Matrix deuterium substitution

The main difficulty in obtaining the vinyl radical is that the species easily loses the hydrogen atom and is converted into acetylene. Nevertheless, a very low concentration of the radical H2C=CH has been achieved (Shepherd et al., 1988) by vacuum UV photolysis of ethylene frozen in an argon matrix, and a Fourier transform IR study of this intermediate has been carried out. A variety of and deuterium-substituted ethylene parent molecules were used to form various isotopomers of vinyl radical. On the basis of its isotopic behaviour and by comparison with ab initio... 

In recent years the associated hydrogen molecular ions have attracted much attention in relation to low temperature chemistry including the chemistry of interstellar clouds. Here we call attention to a recent ESR study by Kumagai et al. [79] on the H2 -core H radical cation with Z)2d symmetry generated and stabihzed in irradiated solid /7-H2 matrix. It is demonstrated that ESR spectroscopy is a very usefiil experimental technique to observe and identify unstable intermediates attributed to hydrogen molecular ions. The assignment of H " radical ions was experimentally confirmed by generating deuterium substituted... 

In the end we deal with a recently reported high-resolution ESR spectrum of H2 -core He radical cation with a D2A symmetry, abbreviated as [H2(H2)H2]", where the H2 in the parentheses is the H2 -core and the two H2 molecules in both ends are the side-on H2 molecules. The 4.2 K y-irradiated pure P-H2 showed hyperfine structure due to two equivalent H-atoms of the H2" -core . The identification and structure of [H2(H2)H2] were confirmed by comparing the experimentally obtained ESR spectra of deuterium substitutions such as [H2(H2)HD], [H2(HD)H2] and [D2(H2)H2] cations generated in irradiated D2/F-H2 and HD/p-H2 mixture systems with ab-initio computations. D-substitution of the side-on H2 molecules such as [H2(H2)HD]" and [D2(H2)D2] is informative because the hf interaction due to the side-on D2 or HD nuclei is observable. For example, [H2(H2)D2] cation gave rise to a quintet of /t/lines due to the 0-D2 with 7=0 and 2 states in addition to the quartet due to the H2" -core . Thus, the [H2(H2)H2] radical cation is concluded to be preferentially generated in irradiated solid p-H2 matrix. 

As indicated previously, the use of deuterium substitution allows the introduction of contrast between these doped molecules and the rest of the hydrogenated matrix. The details of such experiments are discussed elsewhere. 

A thin solution-cast film of a diblock copolymer consisting of a polystyrene block (M 50,000) and a deuterium-substituted polyisoprene block (A/ 100,000) was stimulated at room temperature with a O.r/i-amplitude, 23-Hz dynamic tensile strain. In this composition range, diblock copolymers of styrene and isoprene produce a hexagonally packed regular array of rod-like polystyrene microdomains embedded in a continuous matrix of the polyisoprene block. The diameter of each polystyrene microdomain is well below 0.1 pm. 

Evidence for the formation of the first dizinc(I) salt was observed in 1967 by introducing Zn into molten ZnClj [16]. The existence of Zn2Cl2 was proven by UV-vis, Raman, and ESR (Electron Spin Resonance) spectroscopy as well as magnetic susceptibility measurement and chemical methods however, no crysttJ structure has been obtained yet. Dizinc(l) dihydride, ZnjHj, was claimed to be produced in 1995 by the matrix-isolation technique and could be identified by spectroscopic methods involving deuterium substitution and comparisons with quantum mechanical calculations [17]. 

The method using GC/MS with selected ion monitoring (SIM) in the electron ionization (El) mode can determine concentrations of alachlor, acetochlor, and metolachlor and other major corn herbicides in raw and finished surface water and groundwater samples. This GC/MS method eliminates interferences and provides similar sensitivity and superior specificity compared with conventional methods such as GC/ECD or GC/NPD, eliminating the need for a confirmatory method by collection of data on numerous ions simultaneously. If there are interferences with the quantitation ion, a confirmation ion is substituted for quantitation purposes. Deuterated analogs of each analyte may be used as internal standards, which compensate for matrix effects and allow for the correction of losses that occur during the analytical procedure. A known amount of the deuterium-labeled compound, which is an ideal internal standard because its chemical and physical properties are essentially identical with those of the unlabeled compound, is carried through the analytical procedure. SPE is required to concentrate the water samples before analysis to determine concentrations reliably at or below 0.05 qg (ppb) and to recover/extract the various analytes from the water samples into a suitable solvent for GC analysis. 

Vacuum UV photolysis of SiH4 in an Ar matrix at 4 or 14 K yields the reactive species SiH, SiH2 and SiH3. The analysis of the matrix IR spectra is complicated by the presence of several species along with the starting material SiH4, and substitution by deuterium is of only modest value. 

Both deuterium atoms substituted in a-position. F-matrix elements taken from a model of Wolfsberg and Stern ( normaF diagonal and normal interaction force... 

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