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  • 1
    Electronic Resource
    Electronic Resource
    Modes of phosphate binding to copper(II): investigations of the electron spin echo envelope modulation of complexes on surfaces and in solutions (1990)
    s.l. : American Chemical Society
    Inorganic chemistry 29 (1990), S. 1536-1543 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic00333a019
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  • 2
    Electronic Resource
    Electronic Resource
    EPR, proton and carbon-13 ENDOR, nitrogen-14 ESEEM, and x-ray crystallographic studies of oxovanadium(IV) bis((1R)-3-(heptafluorobutyryl)camphor): a catalyst for asymmetric hetero Diels-Alder reactions (1993)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 115 (1993), S. 1908-1915 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00058a041
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  • 3
    Electronic Resource
    Electronic Resource
    Pulsed electron-nuclear double resonance methodology (1991)
    s.l. : American Chemical Society
    Chemical reviews 91 (1991), S. 1481-1505 
    Details
    ISSN: 1520-6890
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/cr00007a011
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  • 4
    Electronic Resource
    Electronic Resource
    Multiple quantum coherence in HYSCORE spectra (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 9478-9488 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The implementation of matched pulses in two-dimensional electron spin echo envelope modulation experiments results in a drastic increase in intensity of peaks representing nuclear multiple quantum coherence. For a spin system consisting of one electron spin S=〈fraction SHAPE="CASE"〉12 and two nuclei with spin I=〈fraction SHAPE="CASE"〉12 the nuclear coherence created by the sequence (π/2)−τ−(π/2) is calculated. The transfer amplitudes between different kinds of nuclear coherences of a microwave π pulse are given. A new matched HYSCORE pulse sequence, called SMART HYSCORE, is introduced with only one microwave pulse for the generation and detection of nuclear coherence, which does not suffer from blind spots. This sequence is applied to a single crystal and a disordered system, and it is demonstrated how the resolution of weakly coupled nuclei can be increased. Furthermore we show that information about the relative sign of hyperfine couplings and about the relative orientation of the hyperfine tensors can be derived from the ridge patterns in a HYSCORE experiment. The numerical simulations are confirmed experimentally. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1368366
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  • 5
    Electronic Resource
    Electronic Resource
    Right-angle wiggling electron paramagnetic resonance spectroscopy (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 9126-9135 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Right-angle wiggling (RAW) electron paramagnetic resonance (EPR) spectroscopy is introduced. In this two-dimensional pulse EPR technique the orientation of the external magnetic field B0 is varied during the pulse sequence. For this purpose an additional sinusoidal field of variable amplitude ΔB0⊥ is applied perpendicular to the orientation of B0. RAW-EPR is an alternative and experimentally much less demanding technique to right-angle spinning for performing anisotropy-resolved EPR experiments [Sierra and Schweiger, Mol. Phys. 95, 973 (1998)]. It can be applied to improve the resolution of EPR spectra of orientationally disordered systems or to separate overlapping single-crystal EPR spectra, and to facilitate an unambiguous interpretation of these spectra. A detailed theoretical description of RAW-EPR is given. Model calculations for systems with axial and orthorhombic symmetry, as well as a number of RAW-EPR experiments on paramagnetic systems with anisotropic interactions are presented. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1412876
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  • 6
    Electronic Resource
    Electronic Resource
    Nuclear coherence-transfer echoes in pulsed EPR (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 5207-5219 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Nuclear coherence-transfer echoes created in disordered electron–nuclear spin systems by microwave pulses are described. Once nuclear coherence is generated, a nonselective microwave π pulse inverts the electron spins thereby interchanging nuclear coherence between the two electron spin manifolds. This exchange refocuses the inhomogeneity of the secular part of the hyperfine interaction. The mechanisms of echo formation for weak and strong hyperfine couplings are explained by using simple vector diagrams. Various methods to create and detect nuclear coherence by microwave pulses are discussed with special attention directed to the sequence π/2–τ–π/2–t1–π–t2–π/2–τ. In this four-pulse experiment the nuclear coherence-transfer echo is observed as an amplitude modulation of the electron spin echo intensity. The nuclear coherence-transfer echo can be shifted to a time interval fully separated from the one covered by the instrumental deadtime. The time evolution of an S=1/2, I=1/2 model spin system during the four-pulse sequence is described using the density operator formalism. Several one- and two-dimensional four-pulse experiments are discussed on this basis and their spectra are analyzed in terms of nuclear coherence-transfer pathways. A new one-dimensional experiment based on nuclear coherence-transfer echoes, deadtime free ESEEM by nuclear coherence-transfer echoes (DEFENCE) is proposed to exploit undistorted electron spin echo envelope modulation (ESEEM) spectra. DEFENCE is a fast pulsed EPR technique that is unpretentious with respect to the required microwave equipment. The predicted features of the nuclear coherence-transfer echoes and of the DEFENCE approach are verified experimentally. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469246
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  • 7
    Electronic Resource
    Electronic Resource
    S-band (2–4 GHz) pulse electron paramagnetic resonance spectrometer: Construction, probe head design, and performance (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 2807-2817 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design and construction of a combined pulse/continuous wave electron paramagnetic resonance (EPR) spectrometer operating in the 2–4 GHz frequency range (S band) are presented. Details of the microwave bridge are described including a Q-tune arm for adjustments of the microwave coupling during high-power pulse excitation. Factors affecting the microwave resonator construction and the frequency and Q tuning are discussed. The distribution of the electromagnetic field in a bridged loop-gap resonator with a large sample volume for EPR and electron-nuclear double resonance experiments and experiments with B0-field steps are determined using numerical calculations. One- and two-dimensional pulse echo experiments are presented and compared with the results obtained with a pulse X-band (8–10 GHz) spectrometer. For weakly coupled nuclei the echo modulation depth increases by about one order of magnitude when lowering the microwave frequency from X band to S band. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150697
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  • 8
    Electronic Resource
    Electronic Resource
    Hyperfine decoupling in electron spin resonance (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 9979-9991 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new class of experiments is introduced to electron spin resonance (ESR) spectroscopy that utilizes hyperfine decoupling for resolution enhancement and spectrum simplification, and that provides a basis for correlation techniques. A general framework is provided for the discussion of pulse ESR experiments on systems with arbitrary effective electron spin S and an arbitrary number of coupled nuclear spins and is used to describe spin decoupling in pulse ESR and ENDOR spectroscopy. Analytical expressions are given for the hyperfine-decoupled nuclear frequencies and the residual hyperfine splittings of spin-1/2 nuclei during strong decoupling. Pulse sequences are proposed for hyperfine-decoupled electron spin echo envelope modulation (ESEEM) and electron nuclear double resonance (ENDOR) experiments as well as for the correlation of the hyperfine-decoupled ESEEM spectrum with two-pulse and three-pulse ESEEM spectra and of hyperfine-decoupled ENDOR with the hyperfine splittings. It is shown that hyperfine-decoupled ESEEM and ENDOR spectra can reveal information on the magnetic quantum numbers involved in an ESR observer transition, and that choosing a transition mS↔mS+1 with mS≠−1/2 can improve the resolution of a nuclear frequency spectrum. In addition, such experiments can be used to determine the relative signs of hyperfine couplings. The potential of the two-dimensional DECENT (decoupled ESEEM correlated to nuclear transition frequencies) experiment is demonstrated on weakly coupled 14N nuclei in both an ordered and a disordered system and on the hexaquo manganese (II) complex (S=5/2) in a single crystal. It is also shown that for the ESR observer transition mS=(−3/2↔−5/2) the S=5/2 system yields highly resolved hyperfine-decoupled ENDOR spectra which allow for a complete assignment of the ENDOR lines. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474073
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  • 9
    Electronic Resource
    Electronic Resource
    Matched two-pulse electron spin echo envelope modulation spectroscopy (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 2199-2211 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The theory of nonideal microwave pulses acting on electron–nuclear spin systems is extended and applied to optimize the two-pulse electron spin echo envelope modulation (ESEEM) experiment. A superoperator approach for a computationally efficient simulation of experiments involving non-ideal pulses is introduced and the corresponding unitary transformation superoperator is given analytically for a system consisting of one electron spin S=1/2 and one nuclear spin I=1/2. Density operator single-element transfers are divided into allowed and forbidden ones and are classified according to their functioning in pulse ESR. By increasing the efficiency of forbidden transfers by Hartmann–Hahn matching during prolonged pulses, the sensitivity of the conventional two-pulse ESEEM experiment may drastically be improved and discrimination between basic, hyperfine, and combination frequencies becomes possible. The implications of the theory for spin systems with an arbitrary number of nuclear spins 1/2 are investigated by deriving and discussing a general condition for Hartmann–Hahn matching of forbidden transitions. It is shown that the product rule valid for two-pulse echo modulations caused by more than one nucleus does not hold for nonideal pulses. A method is developed that allows one to reduce the thus arising large dimensionality of the diagonalization problem in numerical simulations. The theoretical conclusions are verified by experiments on two transition metal complexes in single crystals and on a spin-label-doped polymer sample. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472087
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  • 10
    Electronic Resource
    Electronic Resource
    The generalized hyperfine sublevel coherence transfer experiment in one and two dimensions (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 2172-2184 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The generalized hyperfine sublevel coherence transfer pulsed ESR experiment is described that consists of a nuclear coherence generator, a first evolution period, a nonselective microwave π pulse, a second evolution period, and a nuclear coherence detector. Several incrementation schemes to perform one-dimensional experiments are discussed, namely, a four-pulse electron spin echo envelope modulation scheme for measuring combination frequencies, two types of nuclear coherence transfer echo experiments (DEFENCE) to record dead time free electron spin echo envelope modulation spectra of disordered systems, and a new hyperfine spectroscopy experiment for the direct measurement of hyperfine frequencies. The one-dimensional experiments can be combined to four two-dimensional schemes. In addition to hyperfine sublevel correlation spectroscopy (HYSCORE) where two nuclear frequency dimensions are correlated, three new two-dimensional experiments are introduced that correlate the hyperfine with the nuclear frequency, the combination frequency with the nuclear frequency, and the combination frequency with the hyperfine frequency. With a properly selected two-dimensional incrementation scheme the digital resolution and signal-to-noise ratio of the spectra can be improved and artifacts can be suppressed. The predicted features of the one- and two-dimensional experiments are verified experimentally for both ordered and disordered systems using echo and coherent Raman beat detection. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470973
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