Hyperfine interactions-un peu d'histoire

Bleaney, B.

doi:10.1007/bf02395979

Cited by 5 publications

(3 citation statements)

References 39 publications

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“…The energy difference between these two sublevels is the quadrupole splitting ∆E Q . In general, for asymmetric field gradients at the nucleus, we have For the ground state of the free Fe 2+ ion 5 D, the valence contribution to the EFG tensor is dominant 37 and can be expressed in terms of equivalent operators L ij as follows [38][39][40] In eq 11, 1 -R is the Sternheimer factor 36 and 〈r -3 〉 is the mean value of r -3 for 3d electrons. 39,40 The expectation values 〈L ij 〉 are evaluated for the orbital ferrous ground state.…”

Section: Introductionmentioning

confidence: 99%

Mössbauer Spectroscopy of the Spin-Coupled Fe³⁺−Fe²⁺ Center of Reduced Uteroferrin

Rodriguez

Xia

et al. 1996

J. Phys. Chem.

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The mixed valence active center of the diiron-oxo protein uteroferrin (Ufr), a porcine purple acid phosphatase, has been analyzed by Mössbauer spectroscopy. Low and high magnetic field spectra are consistent with an antiferromagnetically spin-coupled center. Theoretical spectra that simulate experimental data have been calculated by diagonalizing the spin Hamiltonian H )Here the subscripts 1 and 2 refer to Fe 3+ (S 1 ) 5/2) and Fe 2+ (S 2 ) 2), respectively. For T e 4.2 K, both irons exhibit resolved magnetic hyperfine splittings which depend on the direction and magnitude of the external field, and the static limit of H applies. For T g 100 K, the spin fluctuations are fast and pure quadrupole doublets are observed unless strong fields are applied. In Ufr, the dominant isotropic exchange is strongly perturbed by the zero field splitting (ZFS). We have also calculated the EPR g eff tensor by diagonalizing the electronic terms of H. Our work confirms the claim (Sage, J. T.; et al. J. Am. Chem. Soc. 1989, 111, 7239) that the anisotropy of g eff arises from the admixture of higher spin manifolds to the S eff ) 1 / 2 ground state by the ZFS. In order to find a solution to the Hamiltonian, we searched in its large parameter space with a genetic algorithm. This highly effective searching procedure allowed us to find an optimal parameter set that simultaneously reproduces Mössbauer spectra and EPR g values. The strategies employed for the search in the parameter space of H are discussed. We have determined the exchange constant J ) 34.7 cm -1 , ZFS parameters D 1 ) -0.10 cm -1 , E 1 ≈ 0, D 2 ) +10.81 cm -1 , and E 2 ) +3.17 cm -1 , and hyperfine tensors ã 1 /g n n ) -(21.4,21.2,17.8) T and ã 2 /g n n ) -(15.2,12.2,14.1) T. We have also interpreted the 4.2 K spectra with an effective S eff ) 1 / 2 Hamiltonian for the ground state and determined effective hyperfine tensors Ã 1 eff /g n n ) -(45.6,64.1,31.3) T and Ã 2 eff /g n n ) +(11.4,24.9,16.7) T. For Fe 2+ , the ZFS and the electric and magnetic hyperfine interactions were consistent with the presence of axial and rhombic distortions of the dominant octahedral electrostatic potential. The principal axes of the orthorhombic field, which are rotated by 45°about the z axis of the octahedral field, defined an orbital ground state for Fe 2+ of |x 2 -y 2 〉 symmetry with some |z 2 〉 admixture, consistent with the sign of the electric field gradient. Knowledge of the orbital ground state has allowed us to estimate the intrinsic Fermi contact, orbital, and dipolar hyperfine tensors for Fe 2+ .

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Section: Introductionmentioning

confidence: 99%

Mössbauer Spectroscopy of the Spin-Coupled Fe³⁺−Fe²⁺ Center of Reduced Uteroferrin

Rodriguez

Xia

et al. 1996

J. Phys. Chem.

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“…The direct determination of the nuclear moments of atoms with unpaired electrons is challenging due to the strong magnetic field at the nucleus caused by these electrons. On the other hand this is advantageous, e.g., to obtain sensitively detailed information about the paramagnetism of the respective sample by means of the magnetic resonance in the GHz range [50,53,54,55,56,57]. Nevertheless it has to be considered that exchange interactions [36] average out the hyperfine structure on magnetically undiluted samples [51].…”

Section: Electron Spin Resonance (Esr) and Relations To Isotope Efmentioning

confidence: 99%

Isotope Effects in ESR Spectroscopy

Stößer

Herrmann

2013

Molecules

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In order to present the relationship between ESR spectroscopy and isotope effects three levels are considered: (i) ESR spectroscopy is described on a general level up to the models for interpretation of the experimental spectra, which go beyond the usually used time and mass independent spin-Hamilton operator, (ii) the main characteristics of the generalized isotope effects are worked out, and finally (iii) the basic, mainly quantum mechanical effects are used to describe the coupling of electron spins with the degrees of freedom, which are accessible under the selected conditions, of the respective paramagnetic object under investigation. The ESR parameters and the respective models are formalized so far, that they include the time and mass depending influences and reflect the specific isotope effects. Relations will be established between the effects in ESR spectra to spin relaxation, to spin exchange, to the magnetic isotope effect, to the Jahn-Teller effects, as well as to the influence of zero-point vibrations. Examples will be presented which demonstrate the influence of isotopes as well as the kind of accessible information. It will be differentiated with respect to isotope effects in paramagnetic centres itself and in the respective matrices up to the technique of ESR imaging. It is shown that the use of isotope effects is indispensable in ESR spectroscopy.

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“…The separation between states 1 and 2 is 28 MHz in Fig. 1b and corresponds to the so-called pseudo-nuclear Zeeman effect 9 . For a field strength of 140 G one would expect a splitting of 0.7 MHz between level 1 and 2 by a pure nuclear Zeeman effect.…”

mentioning

confidence: 96%

Energy levels and decoherence properties of single electron and nuclear spins in a defect center in diamond

et al. 2004

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The coherent behavior of the single electron and single nuclear spins of a defect center in diamond and a 13 C nucleus in its vicinity, respectively, are investigated. The energy levels associated with the hyperfine coupling of the electron spin of the defect center to the 13 C nuclear spin are analyzed. Methods of magnetic resonance together with optical readout of single defect centers have been applied in order to observe the coherent dynamics of the electron and nuclear spins. Long coherence times, in the order of µs for electron spins and tens of µs for nuclear spins, recommend the studied system as a good experimental approach for implementing a 2-qubit gate.PACS numbers: 03.65.Yz,03.67.Pp,76.30.Mi Long decoherence time and a precise understanding and manipulation of state evolution are one of the most important requirements to be met by a quantum system in order to implement quantum computing algorithms 1 . For this reasons among all the solid state systems considered for quantum computing, spins are the most promising in respect to long decoherence times and state control. An efficient system for this purpose is given by single paramagnetic defect centers in diamond 2 . Recently, single spin readout in Nitrogen-Vacancy (N-V) defects in diamond was demonstrated 3 . The coherent evolution of the electron spin of a defect center in diamond was previously reported 4 and a two qubit conditional quantum gate was demonstrated 5 . Here, we extend our investigation to the system composed of a single electron spin hyperfine coupled to two nuclei, one 13 C and a 14 N . The Nitrogen-Vacancy (N-V) defect center in diamond is a paramagnetic system (S = 1) consisting of a substitutional 14 N atom next to a vacancy into an adjacent lattice site. The N-V defect center occurs naturally in diamonds containing substitutional nitrogen. The ground and first excited states ( 3 A and 3 E, respectively) of the defect are spin triplets. The center exhibits a strong dipole allowed optical transition between the 3 E and 3 A states, at 637 nm 4 , allowing for its optical detection as a single center. In the absence of an external magnetic field, the ground state is split in the crystal field into a singlet state Z (m s = 0) and a doublet X, Y (m s = ±1), separated by 2.88 GHz. Optically Detected Magnetic Resonance (ODMR) is performed in the continuous wave regime by monitoring the changes in the fluorescence intensity emitted by the optically excited N-V center, upon sweeping the microwaves. At the mw resonance value, 2.88 GHz in zero field, the populations of the ground state spin sublevels will change, leading to a drop in the fluorescence signal (negative ODMR effect) 6 . Experimental work was done with a home-built setup. The confocal microscope operates over a wide range of temperatures (2 to 300 K). Microwaves are transmitted to the sample using an ESR microresonator (provided by D. Suter of University Dortmund). The small size of the diameter of the loop (500 µm) allows to achieve high values for the microwave Rabi frequen...

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Hyperfine interactions-un peu d'histoire

Cited by 5 publications

References 39 publications

Mössbauer Spectroscopy of the Spin-Coupled Fe³⁺−Fe²⁺ Center of Reduced Uteroferrin

Mössbauer Spectroscopy of the Spin-Coupled Fe³⁺−Fe²⁺ Center of Reduced Uteroferrin

Isotope Effects in ESR Spectroscopy

Energy levels and decoherence properties of single electron and nuclear spins in a defect center in diamond

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Hyperfine interactions-un peu d'histoire

Cited by 5 publications

References 39 publications

Mössbauer Spectroscopy of the Spin-Coupled Fe3+−Fe2+ Center of Reduced Uteroferrin

Mössbauer Spectroscopy of the Spin-Coupled Fe3+−Fe2+ Center of Reduced Uteroferrin

Isotope Effects in ESR Spectroscopy

Energy levels and decoherence properties of single electron and nuclear spins in a defect center in diamond

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Product

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Mössbauer Spectroscopy of the Spin-Coupled Fe³⁺−Fe²⁺ Center of Reduced Uteroferrin

Mössbauer Spectroscopy of the Spin-Coupled Fe³⁺−Fe²⁺ Center of Reduced Uteroferrin