M. B. Wise

ESR investigation of matrix isolated B 16O and B 17O radicals: Comparison of nuclear hyperfine structure with ab initio calculations

An extensive ESR investigation of the 2Σ B16O and B17O radicals in rare gas matrices has been conducted. Several different trapping sites in neon matrices have been found and investigated as a function of temperature over the range 3–10 K both during and after deposition. Motional averaging of the nuclear hyperfine tensor seems to be occurring for two neon sites and the argon matrix. The large isotropic boron hyperfine coupling of these sites and the 17O hfs show excellent agreement with ab initio theoretical results. BO radicals trapped in a third neon site do not appear to be undergoing motional behavior. Isotropic and dipolar hyperfine parameters for this site show reasonable agreement with theoretical results. BO radicals in one neon site which is extremely sensitive to temperature effects exhibit nearly perfect ’’single‐crystal‐like’’ preferential orientation which has not been previously observed in rare gas matrix ESR studies. The results of this BO investigation help to correct erroneous conclusio...

The high temperature generation and ESR investigation of ScH2, YH2, and YD2 radicals in rare gas matrices: A nonequilibrium vaporization technique for solid samples

The ScH2, YH2, and YD2 radicals have been generated from metal hydride powders at high temperatures by a nonequilibrium vaporization technique. The MH2 radicals were isolated in rare gas matrices at 12 K and investigated by electron spin resonance (ESR). The vaporization procedure has potential applications for the production of other vapor species which are difficult to generate by conventional means. The electronic structure, geometry, and ground state of these dihydride radicals were estimated from the ESR results and compared with recent theoretical conclusions. The metal ’’d’’ electron was found not to participate significantly in the M–H bond. These findings for MH2 are compared with recent results for ScF2 and YF2. The magnetic parameters for ScH2 are g∥ = 1.980 (1), g⊥ = 1.987 (1), A∥(45Sc) = −212 (2) MHz, A⊥(45Sc) = −128, ‖Aiso‖(H) = 12 (2). For YH2, g⊥ = 1.991  (1), A⊥(89Y) = −40 (10) MHz, ‖A⊥‖ (H) = 13 (2) MHz.

Photolytic codeposition generation of the HgF radical in an argon matrix at 12 K: An ESR investigation

The HgF radical has been generated by photolysis during the codeposition reaction of Hg atoms and F2(g) in an argon matrix at 12 K. The magnetic parameters are g(∥) = 1.993(1), g⊥ = 1.961(1); A∥ (19F) = 1344(10) MHz, A⊥ (19F) = 195(5), A∥ (199Hg) = 22 622(10), A⊥(199Hg) = 21 880(8), A∥ (201Hg) = 8055(12), A⊥ (201Hg) = 7760(10). Utilizing the g and A tensor data, the electronic structure of HgF is compared to the other MF radicals studied.

The generation and ESR investigation of the BeF radical in rare gas matrices

The 13 electron BeF radical has been generated and trapped in argon and krypton matrices at 12 K and studied via ESR spectroscopy. Comparisons are made between BeF and other similar radicals. The calculated dipole moment for BeF is 1.1 D. The magnetic parameters in argon are g∥=2.001, g⊥=2.001, Aiso(Be)=294(2) MHz, and Aiso(19F) =230(2) MHz. The 19F hfs is unusually isotropic for an MF radical, suggesting that rotational averaging might be occurring. Results of ab initio theoretical calculations are compared to the observed A tensors. The BeF molecule was generated by the codeposition of thermally produced Be atoms and molecular fluorine in the rare gas matrices.

ESR investigation of ScF2 isolated in rare gas matrices at 12 K

The radical molecule ScF2 has been produced at high temperature, trapped in argon and xenon matrices at 12 K and studied via electron spin resonance (ESR). Attempts to study the radical in neon matrices at 4 K and nitrogen at 12 K were unsuccessful. The observed 45Sc and 19F hyperfine splittings in an argon matrix were 220 and 28 MHz, respectively. The g tensor was not fully resolved; however, the most intense component had a g value of 1.995 (1) in argon. The magnetic parameters and electronic structure of ScF2 are compared to ScO, ScS, and TiF2+. A nearly tenfold decrease in metal hfs is observed for ScF2 relative to ScO.

Codeposition generation of BeCl in an argon matrix at 12 K: An ESR investigation

The molecular radical BeCl has been produced by the codeposition of beryllium atoms and chlorine in an argon matrix at 12 K. An ESR investigation yields the following magnetic parameters: g∥ = 2.001 (1), g⊥ = 1.998 (1), A∥(Be) = 282 (2) MHz, A⊥(Be) = 268 (2) MHz, ‖A∥‖(35Cl) = 53 (2) MHz, and ‖A⊥‖(35Cl) = 24 (2) MHz. Spin densities obtained from the ESR results are compared with ab initio calculations. The calculations yield a dipole moment of 1.0 D for BeCl. These results for BeCl are compared with BeF, BeOH, and BeH. BeCl, unlike BeF, does not exhibit rotational behavior in an argon matrix.

Generation and ESR investigation of YF2 and Y(CN)2 radicals in rare gas matrices

The YF2 and Y(CN)2 radicals have been generated and trapped in argon and krypton matrices at 12 K and studied via ESR spectroscopy. Codeposition reactions between Y and X2 were found to produce Y(CN)2 but not YF2 which was generated by the high temperature vaporization reduction of YF3. Comparisons of matrix codeposition results with gas phase reactions monitored by electronic chemiluminescence are discussed. The magnetic parameters for YF2 in argon are: g1=1.997(1), g2=1.989(1), and g3=1.985(1): 19F; A1=98(2), A2=89(2), and A3=75(2) MHz: 89Y; A1=758(3), A2=757(3), and A3=728(3) MHz. The parameters for Y(CN)2 are: g=1.973(2) and A(89Y)=672(3). The existence of low lying excited states and correlations with the Y++ ion are discussed as reasons why the electronic structure of YF2 differs substantially from that of ScF2. The electronic differences are consistent with recent entropy measurements for these two radicals.