101
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Mysak ER, Smith JD, Ashby PD, Newberg JT, Wilson KR, Bluhm H. Competitive reaction pathways for functionalization and volatilization in the heterogeneous oxidation of coronene thin films by hydroxyl radicals and ozone. Phys Chem Chem Phys 2011; 13:7554-64. [DOI: 10.1039/c0cp02323j] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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102
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Starr DE, Pan D, Newberg JT, Ammann M, Wang EG, Michaelides A, Bluhm H. Acetone adsorption on ice investigated by X-ray spectroscopy and density functional theory. Phys Chem Chem Phys 2011; 13:19988-96. [DOI: 10.1039/c1cp21493d] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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103
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Bluhm H, Foletti S, Mahalu D, Umansky V, Yacoby A. Enhancing the coherence of a spin qubit by operating it as a feedback loop that controls its nuclear spin bath. PHYSICAL REVIEW LETTERS 2010; 105:216803. [PMID: 21231340 DOI: 10.1103/physrevlett.105.216803] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2010] [Indexed: 05/30/2023]
Abstract
In many realizations of electron spin qubits the dominant source of decoherence is the fluctuating nuclear spin bath of the host material. The slowness of this bath lends itself to a promising mitigation strategy where the nuclear spin bath is prepared in a narrowed state with suppressed fluctuations. Here, this approach is realized for a two-electron spin qubit in a GaAs double quantum dot and a nearly tenfold increase in the inhomogeneous dephasing time T₂* is demonstrated. Between subsequent measurements, the bath is prepared by using the qubit as a feedback loop that first measures its nuclear environment by coherent precession, and then polarizes it depending on the final state. This procedure results in a stable fixed point at a nonzero polarization gradient between the two dots, which enables fast universal qubit control.
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104
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Zhang C, Grass ME, McDaniel AH, DeCaluwe SC, El Gabaly F, Liu Z, McCarty KF, Farrow RL, Linne MA, Hussain Z, Jackson GS, Bluhm H, Eichhorn BW. Measuring fundamental properties in operating solid oxide electrochemical cells by using in situ X-ray photoelectron spectroscopy. NATURE MATERIALS 2010; 9:944-949. [PMID: 20871607 DOI: 10.1038/nmat2851] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Accepted: 08/06/2010] [Indexed: 05/29/2023]
Abstract
Photoelectron spectroscopic measurements have the potential to provide detailed mechanistic insight by resolving chemical states, electrochemically active regions and local potentials or potential losses in operating solid oxide electrochemical cells (SOCs), such as fuel cells. However, high-vacuum requirements have limited X-ray photoelectron spectroscopy (XPS) analysis of electrochemical cells to ex situ investigations. Using a combination of ambient-pressure XPS and CeO(2-x)/YSZ/Pt single-chamber cells, we carry out in situ spectroscopy to probe oxidation states of all exposed surfaces in operational SOCs at 750 °C in 1 mbar reactant gases H(2) and H(2)O. Kinetic energy shifts of core-level photoelectron spectra provide a direct measure of the local surface potentials and a basis for calculating local overpotentials across exposed interfaces. The mixed ionic/electronic conducting CeO(2-x) electrodes undergo Ce(3+)/Ce(4+) oxidation-reduction changes with applied bias. The simultaneous measurements of local surface Ce oxidation states and electric potentials reveal the active ceria regions during H(2) electro-oxidation and H(2)O electrolysis. The active regions extend ~150 μm from the current collectors and are not limited by the three-phase-boundary interfaces associated with other SOC materials. The persistence of the Ce(3+)/Ce(4+) shifts in the ~150 μm active region suggests that the surface reaction kinetics and lateral electron transport on the thin ceria electrodes are co-limiting processes.
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105
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Křepelová A, Huthwelker T, Bluhm H, Ammann M. Surface Chemical Properties of Eutectic and Frozen NaCl Solutions Probed by XPS and NEXAFS. Chemphyschem 2010; 11:3859-66. [DOI: 10.1002/cphc.201000461] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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106
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Whaley JA, McDaniel AH, El Gabaly F, Farrow RL, Grass ME, Hussain Z, Liu Z, Linne MA, Bluhm H, McCarty KF. Note: Fixture for characterizing electrochemical devices in-operando in traditional vacuum systems. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2010; 81:086104. [PMID: 20815633 DOI: 10.1063/1.3479384] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We describe a fixture that allows electrochemical devices to be studied under electrical bias in the type of vacuum systems commonly used in surface science. Three spring-loaded probes provide independent contacts for device operation and the characterization in vacuum or under in situ conditions with reactive gases. We document the robustness of the electrical contacts over large temperature changes and their reliability for conventional electrochemical measurements such as impedance spectroscopy. The optical access provided to the device enables the analysis by many techniques, as we demonstrate using x-ray photoelectron spectroscopy to measure local electrical potentials on a solid-oxide electrolyte device operating at high temperature in near-ambient pressure.
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107
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Jiang P, Porsgaard S, Borondics F, Köber M, Caballero A, Bluhm H, Besenbacher F, Salmeron M. Room-temperature reaction of oxygen with gold: an in situ ambient-pressure X-ray photoelectron spectroscopy investigation. J Am Chem Soc 2010; 132:2858-9. [PMID: 20146473 DOI: 10.1021/ja909987j] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The interaction of O(2) with gold foil and gold nanoparticles grown by thermal deposition on TiO(2)(110) was studied by in situ ambient pressure X-ray photoelectron spectroscopy at room temperature. No spontaneous dissociation of O(2) was observed either on Au foil or on Au nanoparticles up to 1 Torr of O(2). X-ray irradiation, however, is very effective in promoting gold oxidation on both surfaces in the presence of O(2). Our results help reconcile recent conflicting experimental observations regarding the activation of molecular oxygen, which is a crucial issue in Au catalyzed oxidation reactions.
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108
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Gullans M, Krich JJ, Taylor JM, Bluhm H, Halperin BI, Marcus CM, Stopa M, Yacoby A, Lukin MD. Dynamic nuclear polarization in double quantum dots. PHYSICAL REVIEW LETTERS 2010; 104:226807. [PMID: 20867197 DOI: 10.1103/physrevlett.104.226807] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Indexed: 05/29/2023]
Abstract
We theoretically investigate the controlled dynamic polarization of lattice nuclear spins in GaAs double quantum dots containing two electrons. Three regimes of long-term dynamics are identified, including the buildup of a large difference in the Overhauser fields across the dots, the saturation of the nuclear polarization process associated with formation of so-called "dark states", and the elimination of the difference field. We show that in the case of unequal dots, buildup of difference fields generally accompanies the nuclear polarization process, whereas for nearly identical dots, buildup of difference fields competes with polarization saturation in dark states. The elimination of the difference field does not, in general, correspond to a stable steady state of the polarization process.
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109
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Baer MD, Kuo IFW, Bluhm H, Ghosal S. Interfacial behavior of perchlorate versus chloride ions in aqueous solutions. J Phys Chem B 2010; 113:15843-50. [PMID: 19929011 DOI: 10.1021/jp9053154] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In recent years, theoretical as well as experimental studies have presented a novel view of the aqueous interface, wherein hard and/or multiply charged ions are excluded from the interface but large polarizable anions show interfacial enhancement relative to the bulk. The observed trend in the propensity of anions to adsorb at the air/water interface appears to follow an inverse order of the Hofmeister series for anions. This study focuses on experimental and theoretical examination of the partitioning behavior of perchlorate (ClO(4)(-)) and chloride (Cl(-)) ions at the air/water interface. We have used ambient pressure X-ray photoelectron spectroscopy to directly probe the interfacial concentrations of ClO(4)(-) and Cl(-) ions in sodium perchlorate and sodium chloride solutions, respectively. In the case of ClO(4)(-) ion, experimental observations are compared with molecular dynamics simulations utilizing both first principles based interaction potentials as well as polarizable classical force fields. Both the experimental and the theoretical results show enhancement of ClO(4)(-) ion at the interface, compared with the absence of such enhancement in the case of the Cl(-) ion. Our observations are in agreement with the expected trend in the interfacial propensity of anions based on the Hofmeister series.
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110
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Tao F, Dag S, Wang LW, Liu Z, Butcher DR, Bluhm H, Salmeron M, Somorjai GA. Break-Up of Stepped Platinum Catalyst Surfaces by High CO Coverage. Science 2010; 327:850-3. [DOI: 10.1126/science.1182122] [Citation(s) in RCA: 409] [Impact Index Per Article: 29.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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111
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Křepelová A, Newberg J, Huthwelker T, Bluhm H, Ammann M. The nature of nitrate at the ice surface studied by XPS and NEXAFS. Phys Chem Chem Phys 2010; 12:8870-80. [DOI: 10.1039/c0cp00359j] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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112
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El Gabaly F, Grass M, McDaniel AH, Farrow RL, Linne MA, Hussain Z, Bluhm H, Liu Z, McCarty KF. Measuring individual overpotentials in an operating solid-oxide electrochemical cell. Phys Chem Chem Phys 2010; 12:12138-45. [DOI: 10.1039/c003581e] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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113
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Mysak ER, Starr DE, Wilson KR, Bluhm H. Note: A combined aerodynamic lens/ambient pressure x-ray photoelectron spectroscopy experiment for the on-stream investigation of aerosol surfaces. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2010; 81:016106. [PMID: 20113137 DOI: 10.1063/1.3276714] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We discuss a new approach for the measurement of the surfaces of free aerosol particles with diameters from 50 to 1000 nm. Particles in this size range have significant influence on the heterogeneous chemistry in the atmosphere and affect human health. Interfacing an aerodynamic lens to an ambient pressure x-ray photoelectron spectrometer permits measurement of the surface chemical composition of unsupported aerosol particles in real time. We discuss the basic considerations for the design of such an instrument, its current limitations and potentials for improvement. Results from a proof-of-principle experiment on silicon oxide particles with average diameters of 270 nm are shown.
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114
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Bluhm H, Bert JA, Koshnick NC, Huber ME, Moler KA. Spinlike susceptibility of metallic and insulating thin films at low temperature. PHYSICAL REVIEW LETTERS 2009; 103:026805. [PMID: 19659233 DOI: 10.1103/physrevlett.103.026805] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Indexed: 05/28/2023]
Abstract
Susceptibility measurements of patterned thin films at sub-K temperatures were carried out using a scanning SQUID microscope that can resolve signals corresponding to a few hundred Bohr magnetons. Several metallic and insulating thin films, even oxide-free Au films, show a paramagnetic response with a temperature dependence that indicates unpaired spins as the origin. The observed response exhibits a measurable out-of-phase component, which implies that these spins will create 1/f-like magnetic noise. The measured spin density is consistent with recent explanations of low frequency flux noise in SQUIDs and superconducting qubits in terms of spin fluctuations, and suggests that such unexpected spins may be even more ubiquitous than already indicated by earlier measurements. Our measurements set several constraints on the nature of these spins.
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115
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Bluhm H, Koshnick NC, Bert JA, Huber ME, Moler KA. Persistent currents in normal metal rings. PHYSICAL REVIEW LETTERS 2009; 102:136802. [PMID: 19392385 DOI: 10.1103/physrevlett.102.136802] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2008] [Indexed: 05/27/2023]
Abstract
The authors have measured the magnetic response of 33 individual cold mesoscopic gold rings, one ring at a time. The response of some sufficiently small rings has a component that is periodic in the flux through the ring and is attributed to a persistent current. Its period is close to h/e, and its sign and amplitude vary between rings. The amplitude distribution agrees well with predictions for the typical h/e current in diffusive rings. The temperature dependence of the amplitude, measured for four rings, is also consistent with theory. These results disagree with previous measurements of three individual metal rings that showed a much larger periodic response than expected. The use of a scanning SQUID microscope enabled in situ measurements of the sensor background. A paramagnetic linear susceptibility and a poorly understood anomaly around a zero field are attributed to defect spins.
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116
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Knop‐Gericke A, Kleimenov E, Hävecker M, Blume R, Teschner D, Zafeiratos S, Schlögl R, Bukhtiyarov VI, Kaichev VV, Prosvirin IP, Nizovskii AI, Bluhm H, Barinov A, Dudin P, Kiskinova M. Chapter 4 X‐Ray Photoelectron Spectroscopy for Investigation of Heterogeneous Catalytic Processes. ADVANCES IN CATALYSIS 2009. [DOI: 10.1016/s0360-0564(08)00004-7] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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117
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Salmeron M, Bluhm H, Tatarkhanov M, Ketteler G, Shimizu TK, Mugarza A, Deng X, Herranz T, Yamamoto S, Nilsson A. Water growth on metals and oxides: binding, dissociation and role of hydroxyl groups. Faraday Discuss 2009; 141:221-9; discussion 309-46. [DOI: 10.1039/b806516k] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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118
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Ghosal S, Brown MA, Bluhm H, Krisch MJ, Salmeron M, Jungwirth P, Hemminger JC. Ion Partitioning at the Liquid/Vapor Interface of a Multicomponent Alkali Halide Solution: A Model for Aqueous Sea Salt Aerosols. J Phys Chem A 2008; 112:12378-84. [DOI: 10.1021/jp805490f] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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119
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Grass M, Zhang Y, Butcher D, Park J, Li Y, Bluhm H, Bratlie K, Zhang T, Somorjai G. A Reactive Oxide Overlayer on Rhodium Nanoparticles during CO Oxidation and Its Size Dependence Studied by In Situ Ambient-Pressure X-ray Photoelectron Spectroscopy. Angew Chem Int Ed Engl 2008; 47:8893-6. [DOI: 10.1002/anie.200803574] [Citation(s) in RCA: 245] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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120
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Grass M, Zhang Y, Butcher D, Park J, Li Y, Bluhm H, Bratlie K, Zhang T, Somorjai G. A Reactive Oxide Overlayer on Rhodium Nanoparticles during CO Oxidation and Its Size Dependence Studied by In Situ Ambient-Pressure X-ray Photoelectron Spectroscopy. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200803574] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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121
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Deng X, Verdaguer A, Herranz T, Weis C, Bluhm H, Salmeron M. Surface chemistry of Cu in the presence of CO2 and H2O. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:9474-9478. [PMID: 18646877 DOI: 10.1021/la8011052] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The chemical nature of copper and copper oxide (Cu 2O) surfaces in the presence of CO 2 and H 2O at room temperature was investigated using ambient pressure X-ray photoelectron spectroscopy. The studies reveal that in the presence of 0.1 torr CO 2 several species form on the initially clean Cu, including carbonate CO 3 (2) (-), CO 2 (delta-) and C (0), while no modifications occur on an oxidized surface. The addition of 0.1 ML Zn to the Cu results in the complete conversion of CO 2 (delta-) to carbonate. In a mixture of 0.1 torr H 2O and 0.1 torr CO 2, new species are formed, including hydroxyl, formate and methoxy, with H 2O providing the hydrogen needed for the formation of hydrogenated species.
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122
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Nordlund D, Odelius M, Bluhm H, Ogasawara H, Pettersson L, Nilsson A. Electronic structure effects in liquid water studied by photoelectron spectroscopy and density functional theory. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.04.096] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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123
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Huber ME, Koshnick NC, Bluhm H, Archuleta LJ, Azua T, Björnsson PG, Gardner BW, Halloran ST, Lucero EA, Moler KA. Gradiometric micro-SQUID susceptometer for scanning measurements of mesoscopic samples. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2008; 79:053704. [PMID: 18513072 DOI: 10.1063/1.2932341] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We have fabricated and characterized micro-SQUID susceptometers for use in low-temperature scanning probe microscopy systems. The design features the following: a 4.6 mum diameter pickup loop; an integrated field coil to apply a local field to the sample; an additional counterwound pickup-loop/field-coil pair to cancel the background signal from the applied field in the absence of the sample; modulation coils to allow setting the SQUID at its optimum bias point (independent of the applied field), and shielding and symmetry that minimizes coupling of magnetic fields into the leads and body of the SQUID. We use a SQUID series array preamplifier to obtain a system bandwidth of 1 MHz. The flux noise at 125 mK is approximately 0.25 mu Phi 0/ sqrt Hz above 10 kHz, with a value of 2.5 mu Phi 0/ sqrt Hz at 10 Hz. The nominal sensitivity to electron spins located at the center of the pickup loop is approximately 200 muB/ sqrt Hz above 10 kHz, in the white-noise frequency region.
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124
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Andersson K, Ketteler G, Bluhm H, Yamamoto S, Ogasawara H, Pettersson LGM, Salmeron M, Nilsson A. Autocatalytic Water Dissociation on Cu(110) at Near Ambient Conditions. J Am Chem Soc 2008; 130:2793-7. [DOI: 10.1021/ja073727x] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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125
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Starr DE, Wong EK, Worsnop DR, Wilson KR, Bluhm H. A combined droplet train and ambient pressure photoemission spectrometer for the investigation of liquid/vapor interfaces. Phys Chem Chem Phys 2008; 10:3093-8. [DOI: 10.1039/b800717a] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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126
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Bluhm H, Moler KA. Dissipative cryogenic filters with zero dc resistance. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2008; 79:014703. [PMID: 18248056 DOI: 10.1063/1.2835716] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The authors designed, implemented, and tested cryogenic rf filters with zero dc resistance, based on wires with a superconducting core inside a resistive sheath. The superconducting core allows low frequency currents to pass with negligible dissipation. Signals above the cutoff frequency are dissipated in the resistive part due to their small skin depth. The filters consist of twisted wire pairs shielded with copper tape. Above approximately 1 GHz, the attenuation is exponential in omega, as typical for skin depth based rf filters. By using additional capacitors of 10 nF per line, an attenuation of at least 45 dB above 10 MHz can be obtained. Thus, one single filter stage kept at mixing chamber temperature in a dilution refrigerator is sufficient to attenuate room temperature black body radiation to levels corresponding to 10 mK above about 10 MHz.
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127
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Brown MA, D’Auria R, Kuo IFW, Krisch MJ, Starr DE, Bluhm H, Tobias DJ, Hemminger JC. Ion spatial distributions at the liquid–vapor interface of aqueous potassium fluoride solutions. Phys Chem Chem Phys 2008; 10:4778-84. [DOI: 10.1039/b807041e] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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128
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Koshnick NC, Bluhm H, Huber ME, Moler KA. Fluctuation Superconductivity in Mesoscopic Aluminum Rings. Science 2007; 318:1440-3. [DOI: 10.1126/science.1148758] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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129
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Nordlund D, Ogasawara H, Bluhm H, Takahashi O, Odelius M, Nagasono M, Pettersson LGM, Nilsson A. Probing the electron delocalization in liquid water and ice at attosecond time scales. PHYSICAL REVIEW LETTERS 2007; 99:217406. [PMID: 18233257 DOI: 10.1103/physrevlett.99.217406] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2007] [Indexed: 05/23/2023]
Abstract
We determine electron delocalization rates in liquid water and ice using core-hole decay spectroscopy. The hydrogen-bonded network delocalizes the electrons in less than 500 as. Broken or weak hydrogen bonds--in the liquid or at the surface of ice--provide states where the electron remains localized longer than 20 fs. These asymmetrically bonded water species provide electron traps, acting as a strong precursor channel to the hydrated electron.
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130
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Chung SB, Bluhm H, Kim EA. Stability of half-quantum vortices in p(x)+ip(y) superconductors. PHYSICAL REVIEW LETTERS 2007; 99:197002. [PMID: 18233107 DOI: 10.1103/physrevlett.99.197002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Indexed: 05/25/2023]
Abstract
We consider the stability conditions for half-quantum vortices in a quasi-two-dimensional p{x}+ip{y} superconductor (such as Sr2RuO4 is believed to be). The predicted exotic nature of these excitations has recently attracted much attention, but they have not been observed yet. We emphasize that an isolated half-quantum vortex has a divergent energy cost in the bulk due to its unscreened spin current, which requires two half-quantum vortices with opposite spin winding to pair. We show that the stability of such a pair is enhanced when the ratio of spin superfluid density to superfluid density rho{sp}/rho{s} is small. We propose using various mesoscopic geometries to stabilize and observe these exotic excitations.
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131
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Verdaguer A, Weis C, Oncins G, Ketteler G, Bluhm H, Salmeron M. Growth and structure of water on SiO2 films on Si Investigated by Kelvin probe microscopy and in Situ X-ray spectroscopies. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:9699-703. [PMID: 17696552 DOI: 10.1021/la700893w] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The growth of water on thin SiO2 films on Si wafers at vapor pressures between 1.5 and 4 Torr and temperatures between -10 and 21 degrees C has been studied in situ using Kelvin probe microscopy and X-ray photoemission and absorption spectroscopies. From 0 to 75% relative humidity (RH), water adsorbs forming a uniform film 4-5 layers thick. The surface potential increases in that RH range by about 400 mV and remains constant upon further increase of the RH. Above 75% RH, the water film grows rapidly, reaching 6-7 monolayers at around 90% RH and forming a macroscopic drop near 100%. The O K-edge near-edge X-ray absorption spectrum around 75% RH is similar to that of liquid water (imperfect H-bonding coordination) at temperatures above 0 degrees C and is ice-like below 0 degrees C.
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132
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Verdaguer A, Sacha GM, Bluhm H, Salmeron M. Molecular structure of water at interfaces: wetting at the nanometer scale. Chem Rev 2007; 106:1478-510. [PMID: 16608188 DOI: 10.1021/cr040376l] [Citation(s) in RCA: 294] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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133
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Gupta SB, Bluhm H. Pulsed underwater corona discharges as a source of strong oxidants: *OH and H2O2. WATER SCIENCE AND TECHNOLOGY : A JOURNAL OF THE INTERNATIONAL ASSOCIATION ON WATER POLLUTION RESEARCH 2007; 55:7-12. [PMID: 17674820 DOI: 10.2166/wst.2007.381] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Because of undesirable side effects of chemical methods pulsed underwater corona discharges are emerging as a potential future advanced oxidation process (AOP) for water disinfection. In pulsed corona discharges a discharge channel is created, which contains a non-thermal plasma with a low degree of ionisation and low electron densities, but with electron energies of up to 10 eV. It has been demonstrated that electrons with this energy can dissociate water and oxygen molecules and produce various reactive radicals (*OH, H*, O*, HO2*), molecular species (H2O2, H2, O2), ultraviolet radiation and shock waves. It is supposed that the combination of all effects leads to a very efficient killing of microorganisms. To understand this in detail and to improve the efficiency of the overall system there is the need to develop suitable diagnostic methods for the quantitative determination of the various oxidants produced during the discharge. In this paper we present preliminary experimental results obtained with different chemical probes for *OH radicals, and H2O2 produced by pulsed corona discharges.
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134
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Bluhm H, Koshnick NC, Huber ME, Moler KA. Magnetic response of mesoscopic superconducting rings with two order parameters. PHYSICAL REVIEW LETTERS 2006; 97:237002. [PMID: 17280232 DOI: 10.1103/physrevlett.97.237002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2006] [Indexed: 05/13/2023]
Abstract
The magnetic response and fluxoid transitions of superconducting aluminum rings of various sizes, deposited under conditions likely to generate a layered structure, show good agreement with a two-order-parameter Ginzburg-Landau model. For intermediate couplings, we find metastable states that have different phase winding numbers around the ring in each of the two order parameters. Those states, previously theoretically predicted, are analogous to fractional vortices in singly connected samples with two-order-parameter superconductivity. Larger coupling locks the relative phase so that the two order parameters are only manifest in the temperature dependence of the response. With increasing proximitization, this signature gradually disappears.
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Willneff EA, Braun S, Rosenthal D, Bluhm H, Hävecker M, Kleimenov E, Knop-Gericke A, Schlögl R, Schroeder SLM. Dynamic Electronic Structure of a Au/TiO2 Catalyst under Reaction Conditions. J Am Chem Soc 2006; 128:12052-3. [PMID: 16967939 DOI: 10.1021/ja062792o] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The electronic structure of a highly active Au/TiO2 powder catalyst was probed in situ by synchrotron X-ray photoelectron spectroscopy (XPS) in the 10-1 mbar range. The electronic structure of the Au component was found to respond sensitively to changes in temperature and indicated the absence of bulklike metallic Au under the conditions of highest catalytic activity. Concurrent modification of interfacial sites adjacent to Au on the TiO2 support was not evident from the Ti photoemission, but may have been below the detection limit of XPS.
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Takahashi O, Odelius M, Nordlund D, Nilsson A, Bluhm H, Pettersson LGM. Auger decay calculations with core-hole excited-state molecular-dynamics simulations of water. J Chem Phys 2006; 124:64307. [PMID: 16483207 DOI: 10.1063/1.2166234] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report a new theoretical procedure for calculating Auger decay transition rates including effects of core-hole excited-state dynamics. Our procedure was applied to the normal and first resonant Auger processes of gas-phase water and compared to high-resolution experiments. In the normal Auger decay, calculated Auger spectra were found to be insensitive to the dynamics, while the repulsive character of the first resonant core-excited state makes the first resonantly excited Auger decay spectra depend strongly on the dynamics. The ultrafast dissociation of water upon O(1s)-->4a(1) excitation was analyzed and found to be very sensitive to initial vibrational distortions in the ground state which furthermore affect the excitation energy. Our calculated spectra reproduce the experimental Auger spectra except for the Franck-Condon vibrational structure which is not included in the procedure. We found that the Auger decay of OH and O fragments contributes to the total intensity, and that the contribution from these fragments increases with increasing excitation energy.
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Ketteler G, Ogletree DF, Bluhm H, Liu H, Hebenstreit ELD, Salmeron M. In Situ Spectroscopic Study of the Oxidation and Reduction of Pd(111). J Am Chem Soc 2005; 127:18269-73. [PMID: 16366581 DOI: 10.1021/ja055754y] [Citation(s) in RCA: 194] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Using a photoemission spectroscometer that operates close to ambient conditions of pressure and temperature we have determined the Pd-O phase diagram and the kinetic parameters of phase transformations. We found that on the (111) surface oxidation proceeds by formation of stable and metastable structures. As the chemical potential of O2 increases chemisorbed oxygen forms followed by a thin surface oxide. Bulk oxidation is a two-step process that starts with the metastable growth of the surface oxide into the bulk, followed by a first-order transformation to PdO.
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Matsushita Y, Bluhm H, Geballe TH, Fisher IR. Evidence for charge Kondo effect in superconducting Tl-doped PbTe. PHYSICAL REVIEW LETTERS 2005; 94:157002. [PMID: 15904175 DOI: 10.1103/physrevlett.94.157002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2004] [Indexed: 05/02/2023]
Abstract
We report results of low-temperature thermodynamic and transport measurements of Pb1-xTlxTe single crystals for Tl concentrations up to the solubility limit of approximately x=1.5%. For all doped samples, we observe a low-temperature resistivity upturn that scales in magnitude with the Tl concentration. The temperature and field dependence of this upturn are consistent with a charge Kondo effect involving degenerate Tl valence states differing by two electrons, with a characteristic Kondo temperature T(K) approximately 6 K. The observation of such an effect supports an electronic pairing mechanism for superconductivity in this material and may account for the anomalously high T(c) values.
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Ghosal S, Hemminger JC, Bluhm H, Mun BS, Hebenstreit ELD, Ketteler G, Ogletree DF, Requejo FG, Salmeron M. Electron Spectroscopy of Aqueous Solution Interfaces Reveals Surface Enhancement of Halides. Science 2005; 307:563-6. [PMID: 15681380 DOI: 10.1126/science.1106525] [Citation(s) in RCA: 418] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Chalcogenide aerogels based entirely on semiconducting II-VI or IV-VI frameworks have been prepared from a general strategy that involves oxidative aggregation of metal chalcogenide nanoparticle building blocks followed by supercritical solvent removal. The resultant materials are mesoporous, exhibit high surface areas, can be prepared as monoliths, and demonstrate the characteristic quantum-confined optical properties of their nanoparticle components. These materials can be synthesized from a variety of building blocks by chemical or photochemical oxidation, and the properties can be further tuned by heat treatment. Aerogel formation represents a powerful yet facile method for metal chalcogenide nanoparticle assembly and the creation of mesoporous semiconductors.
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Borgna A, Anderson BG, Saib AM, Bluhm H, Hävecker M, Knop-Gericke A, Kuiper AET(T, Tamminga Y, Niemantsverdriet JW(H. Pt−Co/SiO2 Bimetallic Planar Model Catalysts for Selective Hydrogenation of Crotonaldehyde. J Phys Chem B 2004. [DOI: 10.1021/jp040286k] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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141
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Morales F, de Groot FMF, Glatzel P, Kleimenov E, Bluhm H, Hävecker M, Knop-Gericke A, Weckhuysen BM. In Situ X-ray Absorption of Co/Mn/TiO2 Catalysts for Fischer−Tropsch Synthesis. J Phys Chem B 2004. [DOI: 10.1021/jp0403846] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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142
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Bluhm H, Hävecker M, Knop-Gericke A, Kleimenov E, Schlögl R, Teschner D, Bukhtiyarov VI, Ogletree DF, Salmeron M. Methanol Oxidation on a Copper Catalyst Investigated Using in Situ X-ray Photoelectron Spectroscopy. J Phys Chem B 2004. [DOI: 10.1021/jp040080j] [Citation(s) in RCA: 187] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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143
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Heijboer WM, Battiston AA, Knop-Gericke A, Hävecker M, Mayer R, Bluhm H, Schlögl R, Weckhuysen BM, Koningsberger DC, de Groot FMF. In-Situ Soft X-ray Absorption of Over-exchanged Fe/ZSM5. J Phys Chem B 2003. [DOI: 10.1021/jp034125c] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Hävecker M, Mayer RW, Knop-Gericke A, Bluhm H, Kleimenov E, Liskowski A, Su D, Follath R, Requejo FG, Ogletree DF, Salmeron M, Lopez-Sanchez JA, Bartley JK, Hutchings GJ, Schlögl R. In Situ Investigation of the Nature of the Active Surface of a Vanadyl Pyrophosphate Catalyst during n-Butane Oxidation to Maleic Anhydride. J Phys Chem B 2003. [DOI: 10.1021/jp027259j] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Heijboer WM, Battiston AA, Knop-Gericke A, Hävecker M, Bluhm H, Weckhuysen BM, Koningsberger DC, de Groot FMF. Redox behaviour of over-exchanged Fe/ZSM5 zeolites studied with in-situ soft X-ray absorption spectroscopy. Phys Chem Chem Phys 2003. [DOI: 10.1039/b306130m] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Gansäuer A, Bluhm H. Reagent-controlled transition-metal-catalyzed radical reactions. Chem Rev 2000; 100:2771-88. [PMID: 11749305 DOI: 10.1021/cr9902648] [Citation(s) in RCA: 338] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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148
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Bluhm H, Salmeron M. Growth of nanometer thin ice films from water vapor studied using scanning polarization force microscopy. J Chem Phys 1999. [DOI: 10.1063/1.479987] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Gansäuer A, Lauterbach T, Bluhm H, Noltemeyer M. A Catalytic Enantioselective Electron Transfer Reaction: Titanocene-Catalyzed Enantioselective Formation of Radicals from meso-Epoxides. Angew Chem Int Ed Engl 1999; 38:2909-2910. [PMID: 10540389 DOI: 10.1002/(sici)1521-3773(19991004)38:19<2909::aid-anie2909>3.0.co;2-y] [Citation(s) in RCA: 116] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A rationally designed titanium(III) catalyst allows the opening of epoxides with high enantioselectivity. This reaction [Eq. (1)] constitutes the first example of an enantioselective transition metal catalyzed radical reaction that proceeds by electron transfer.
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Schwarz A, Schwarz UD, Bluhm H, Wiesendanger R. Determination of miller indices of side faces of small crystallites from scanning force microscopy angle measurements. SURF INTERFACE ANAL 1995. [DOI: 10.1002/sia.740230613] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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