On microwave discharge sources of new chemical species for matrix‐isolation spectroscopy and the identification of charged species
15 Aug 1976-Journal of Chemical Physics (American Institute of Physics)-Vol. 65, Iss: 4, pp 1244-1249
TL;DR: In this paper, the authors investigated the mechanism for trapping new chemical species by condensing the products of a microwave discharge with inert matrices and found that the major product species, HCl2 radical or anion, was formed under conditions where neither ions nor atomic species produced in the discharge were condensed in the matrix.
Abstract: The mechanism for trapping new chemical species by condensing the products of a microwave discharge with inert matrices has been investigated. Variation of geometrical, electrical, and chemical parameters of the Ar, HCl, Cl2 system indicated that the major product species—HCl2 radical or anion—was formed under conditions where neither ions nor atomic species produced in the discharge were condensed in the matrix. The mechanism for forming the product species is vacuum ultraviolet photolysis of the sample during deposition with radiation from the microwave discharge, since a coaxial orifice discharge tube provided photolysis and produced the product species, while studies with an off‐axis orifice discharge tube, which could not serve as a photolysis source, did not produce the product. The H atom–Cl2 reaction gave HCl using both discharge tubes, but the HClx2 species was produced only with the coaxial tube. Hence, this species requires vacuum ultraviolet light in addition to H and Cl atoms for its producti...
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TL;DR: This work has highlighted the importance of knowing the carrier and removal status of materials before they are exposed to each other in the intermediate stages of decomposition.
Abstract: 3.1. Sc Group 6772 3.2. Ti Group 6773 3.3. V Group 6775 3.4. Cr Group 6776 3.5. Mn Group 6777 3.6. Fe Group 6779 3.7. Co Group 6780 3.8. Ni Group 6782 3.9. Cu Group 6782 3.10. Zn Group 6784 3.11. Lanthanide Group 6784 3.12. Actinide Group 6785 3.13. Periodic Trends on Bonding and Reactivity 6785 4. Ionic Mononuclear Transition Metal Oxide Species 6787 4.1. Cations 6788 4.2. Anions 6790 4.2.1. Monoxide Anions 6790 4.2.2. Dioxide Anions 6791 4.2.3. Oxygen-Rich Anions 6792 5. Multinuclear Transition Metal Oxide Clusters 6792 5.1. Sc Group 6793 5.2. Ti Group 6793 5.3. V Group 6793 5.4. Cr Group 6797 5.5. Mn Group 6798 5.6. Fe Group 6798 5.7. Co Group 6798 5.8. Ni Group 6798 5.9. Cu Group 6799 6. Summary 6800 7. Acknowledgments 6800 8. References 6800
330 citations
TL;DR: Minimum energy structures and vibrational frequencies predicted by Density Functional Theory agree with the experimental results, strongly supporting the identification of novel binary transition metal hydride species, which the matrix-isolation method is well-suited to investigate.
Abstract: Metal hydrides are of considerable importance in chemical synthesis as intermediates in catalytic hydrogenation reactions. Transition metal atoms react with dihydrogen to produce metal dihydrides or dihydrogen complexes and these may be trapped in solid matrix samples for infrared spectroscopic study. The MH2 or M(H2) molecules so formed react further to form higher MH4, (H2)MH2, or M(H2)2, and MH6, (H2)2MH2, or M(H2)3 hydrides or complexes depending on the metal. In this critical review these transition metal and dihydrogen reaction products are surveyed for Groups 3 though 12 and the contrasting behaviour in Groups 6 and 10 is discussed. Minimum energy structures and vibrational frequencies predicted by Density Functional Theory agree with the experimental results, strongly supporting the identification of novel binary transition metal hydride species, which the matrix-isolation method is well-suited to investigate. 104 references are cited.
297 citations
TL;DR: In this article, the authors show the participation of rare gas atom(s) in these new compounds, based on studies of the thermally generated species in mixed rare gas matrices, and their vibrational spectra are discussed and compared with those calculated with ab initio methods.
Abstract: Ultraviolet‐irradiation of hydrogen halide containing rare gas matrices yields the formation of linear centrosymmetric cations of type (XHX)+, (X=Ar, Kr, Xe). Annealing of the irradiated doped solids produces, along with thermoluminescence, extremely strong absorptions in the 1700–1000 cm−1 region. Based on isotopic substitution and halogen dependence of these bands, the presence of hydrogen and halogen atom(s) in these species is evident. In the present paper we show the participation of rare gas atom(s) in these new compounds. The evidence is based on studies of the thermally generated species in mixed rare gas matrices. The new species are assigned as neutral charge‐transfer molecules HX+Y− (Y=halogen), and their vibrational spectra are discussed and compared with those calculated with ab initio methods. This is the first time hydrogen and a rare gas atom has been found to make a chemical bond in a neutral stable compound. The highest level ab initio calculations on the existence of compounds of type HXY corroborate the experimental observations. The mechanism responsible for the formation of these species is also discussed.
268 citations
TL;DR: 1. Electron Spin Resonance 2116 2. Infrared and Optical Absorption 2117 3. Laser-Induced Fluorescence 2119 II.
Abstract: 1. Electron Spin Resonance 2116 2. Infrared and Optical Absorption 2117 3. Laser-Induced Fluorescence 2119 III. Quantum Hosts 2122 IV. Matrix Isolation Spectroscopy of Molecular Ions 2124 A. Ion Sources for Matrix Isolation Spectroscopy 2124 B. Spectroscopic Methods 2126 1. Electron Spin Resonance 2126 2. Infrared and Optical Absorption 2126 3. Laser-Induced Fluorescence 2127 V. Deposition of Mass-Selected Species 2128 VI. Summary 2130
176 citations
TL;DR: In this article, the authors identified new molecular anions from matrix infrared spectra with isotopic substitution (HD, D(2), and H(2) + D (2)) and comparison to frequencies calculated by density functional theory.
Abstract: Gold is noble, but excited gold is reactive. Reactions of laser-ablated copper, silver, and gold with H(2) in excess argon, neon, and pure hydrogen during condensation at 3.5 K give the MH molecules and the (H(2))MH complexes as major products and the MH(2)(-) and AuH(4)(-) anions as minor products. These new molecular anions are identified from matrix infrared spectra with isotopic substitution (HD, D(2), and H(2) + D(2)) and comparison to frequencies calculated by density functional theory. The stable linear MH(2)(-) anions are unique in that their corresponding neutral MH(2) molecules are higher in energy than M + H(2) and thus unstable to M + H(2) decomposition. Infrared spectra are observed for the bending modes of AuH(2), AuHD, and AuD(2) in solid H(2), HD, and D(2), respectively. The observation of square-planar AuH(4)(-) attests the stability of the higher Au(III) oxidation state for gold. The synthesis of CuH(2)(-) in solid compounds has potential for use in hydrogen storage.
83 citations
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136 citations
TL;DR: In this paper, the quenching of excited inert gas atoms by N 2 O, O 3, Cl 2 and CCl 4 was observed from the bound upper states of ArO, KrO and ArCl.
136 citations
TL;DR: Intense atomic lines (O, N, S, C, Br, Cl, H, Se, Kr) have been produced by microwave excitation of mixtures of various gases in helium under flow conditions, suitable for atomic emission studies and as photochemical light sources in the vacuum uv.
Abstract: Intense atomic lines (O, N, S, C, Br, Cl, H, Se, Kr) have been produced by microwave excitation of mixtures of various gases in helium under flow conditions. The intensities generally obtained are greater than 10(14) quanta/sec and are suitable for atomic emission studies and as photochemical light sources in the vacuum uv. Conditions for producing these high purity line sources are discussed.
134 citations
TL;DR: In this article, it was shown that the argon absorption is due to hydrogen atoms trapped in Oh interstitial sites in an undistorted inert gas lattice and not due to HAr, HAr+ or HAr2+.
Abstract: Infrared absorptions are reported in the spectra of inert gas‐hydrogen matrix samples which were deposited after the gas mixture passed through a glow discharge. For hydrogen in argon, absorption is recorded at 905 cm−1. This band shifts to 644 cm−1 for deuterium in argon and no new bands are observed with hydrogen‐deuterium mixtures. With krypton matrix, similar absorptions are observed at 852 cm−1 (H2–Kr) and at 607 (D2–Kr). Prolonged infrared irradiation in the spectral range of the absorptions causes them to disappear, the hydrogen absorptions more rapidly than the deuterium features. No similar bands could be detected when xenon or neon matrixes were used. The very small 36Ar–40 Ar isotopic shift (0.2±0.1 cm−1) shows that the argon absorptions cannot be attributed to HAr, to HAr+ or to HAr2+. The evidence is consistent with the interpretation that both in argon and in krypton, the absorptions are due to hydrogen atoms trapped in Oh interstitial sites in an undistorted inert gas lattice. This interpre...
128 citations
125 citations