Nuclear Magnetic Hyperfine Research Articles

The hyperfine spectrum of LiF

The molecular beam electric resonance technique has been used to examine the hyperfine spectrum of 7Li 19F in vibrational states v = 0–4 and rotational states J = 1–6, in addition to a few 6Li 19F lines. With the low electric fields used, the spectrum consists of many overlapping lines which have been deconvoluted by fitting the actual Rabi lineshape. The fitting process includes corrections for the small residual Stark shifts in the frequencies, yielding a precision on the order of a few hertz. By fitting the spectrum, new values have been obtained for the nuclear electric quadrupole and magnetic hyperfine parameters, including their dependence on vibrational and rotational state.

M�ssbauer study of crystallization of glasses in the system K2O-Na2O-CaO-MgO-Al2O3-SiO2

Mossbauer spectroscopy has been used to study several glasses and glass ceramics based on the system K2O-Na2O-CaO-MgO-Al2O3-SiO2 with additions of Fe2O3, Fe3O4 and P2O5. The change of co-ordination and proportion of Fe2+ and Fe3+ occurring during the transformation from glass to glass ceramic was studied. By means of the nuclear magnetic hyperfine splitting effect Fe3O4 was found in glass ceramics with more than 2% of P2O5. The amount of Fe3O4 formed was found to increase with P2O5 addition, but Fe3O4 was not identified in the glass with no P2O5 addition.

The permanent dipole moment of TiN and the nuclear magnetic hyperfine structure in its X 2Σ+ and A 2Π electronic states

The permanent dipole moment of TiN in its X 2Σ+ and A 2Σ states has been determined from the complete resolution of the first- and second-order Stark splitting of the Q21(1.5)+R2(0.5) line of the (0,0) band of the A 2Π–X 2Σ+ system. Values of 3.56±0.05 D (2σ) and 4.63±0.04 D (2σ) have been derived for the X and A states respectively, from least-squares fits to plots of Stark splitting vs electric field strength. Electric fields up to 12 kV/cm have been employed avoiding voltage breakdown. The zero-field spectrum shows resolution of the nuclear magnetic hyperfine structure of the 47TiN and 49TiN isotopes. This hyperfine structure is that of the ground X 2Σ+ state only and is shown to follow closely the coupling case bβS. The value of the Fermi contact parameter is −570 MHz which implies a 4s occupation of the 9σ molecular orbital (MO) of 72%. The results are compared with calculated and available experimental values for early first-row transition metal oxides and nitrides.

NMR study of 63,65 Cu in YBa 2 Cu 3 O 7 to 6.65 single crystals

Abstract We report 63 Cu NMR nuclear spin-lattice relaxation rates (NSLRR) and magnetic hyperfine shift (K cc ) of copper Cu(2) in the CuO 2 planes of YBa 2 Cu 3 O 7−δ as a function of temperature and δ. The independence of K cc and NSLRR (above 120 K) on δ associated with the existence of localized Cu(3d) holes. We comment on the difference in the NSLRR between the δ = 0 and δ ≠ 0 samples which appear below 120 K. It is interpreted as an indirect consequence of the changes in the oxygen 2p electronic band caused by the introduction of oxygen vacancies in the system.

NMR and other magnetic resonance techniques in unstable magnets

This paper reviews and compares the use of nuclear magnetic resonance (NMR) and related hyperfine techniques [muon spin rotation (μSR) and, to a lesser extent, other methods] in the study of 4f and 5f magnetism in “unstable magnets”, i.e., intermediate-valent and heavy-fermion materials. In both NMR and μSR the features of interest are the spectral shape, the frequency shiftK (Knight shift in metals) and the spin-lattice relaxation rate 1/T1. For temperatures below the characteristic or “Kondo” temperatureT0 these experiments given evidence for (1) modification of the transferred hyperfine field [nonlinearK(χ)]. (2) spin fluctuations with a characteristic fluctuation rate ∼kBT0/h, (3) strong energy-gap anisotropy (zeros of the gap along lines on the Fermi surface) in heavy-fermion superconductors, (4) spin-singlet Cooper pairing from the change in muon Knight shift in superconducting UBe13, and (5) very weak static magnetism (10−1–10−3 μB/f atom) in CeAl3, CeCu2Si2, U1−xThxBe13 (x=0.033), and UPt3. There is some controversy concerning the interpretation of 1/T1 well aboveT0 in UBe13; the situation is reviewed.

Low temperature calorimetric and magnetic properties of Al-Mn and Al-Mn-Si quasi-crystals

We report on the low temperature specific heat C p and magnetic measurements for the following Al-Mn alloys: solid solution Al-3at.%Mn, Al 86Mn 14 and Al 75Mn 20Si 5 in quasi-crystalline phases. From the amplitude of the electronic specific heat determined below 0.3 K, we propose, in agreement with the electrical resistivity values, that the large density of states in the quasi-crystalline phases are due to virtual bound states related to a regime of isolated manganese “impurities”. Both C p and magnetic measurements indicate a rapid evolution of the magnetic interactions from Al 86Mn 14 to Al 75Mn 20Si 5. In the latter, the ξ ac data together with the nuclear magnetic hyperfine specific heat confirm a spin glass state similar to that of canonical spin glasses such as Cu-Mn and Au-Mn. We emphasize that a small fraction of Mn s atoms are magnetic sites (probably less than 10%) in both quasi-crystalline phases.

Magnetism of Eu(BrO 3) 3·9H 2O and the crystal field

Crystals of hydrated europium bromate were grown and magnetic susceptibilities measured from room down to liquid oxygen temperatures. The effective magnetic moment p eff is found todecrease with decreasing temperature indicating a Van Vleck high temperature contribution. The magnetic anisotropy Δ χ= χ‖− χ ⊥ is negative and appreciable. The magnetic susceptibilities χ ‖; and χ ⊥ parallel and perpendicular to c-axis, respectively, rise slowly with decreasing temperature, and around 115 K χ ⊥ becomes nearly constant while χ ‖ decrease slightly; this is quite in contrast to the behavior of other rare earth bromates. A crystal field conforming to D 3h symmetry provided a satisfactory explanation to the observed magnetic behavior. The crystal field parameters used are B 20=175, B 40=−304, B 60=−864 and B 66=910 all in cm −1. The Schottky heat capacity C s does not display any anomaly and vanishes below 50 K. Nuclear quadrupole and magnetic hyperfine splitting due to the crystal field has been worked out. The hyperfine heat capacity for both isotopes shows Schottky anomaly below 2 mK.

Fine and hyperfine structure in the X2Σ + state of gas-phase yttrium monoxide

The A 2Π r- X 2Σ + visible spectrum of gas-phase yttrium monoxide has been studied at sub-Doppler resolution to obtain information on the spin-rotation and 89Y nuclear magnetic hyperfine interactions. The observations were fitted to an effective Hamiltonian model that neglected the nuclear magnetic hyperfine interactions in the excited electronic state. An interpretation of the determined parameters in terms of possible electronic configurations is presented.

An intermodulated fluorescence study of the A2Σ−-X2Πi band system of copper monoxide

Abstract Several lines in the A 2 Σ − ( v = 0)- X 2 Π i ( v = 0) visible band system of gas phase copper monoxide have been measured at sub-Doppler resolution using the technique of intermodulated fluorescence. The copper nuclear magnetic hyperfine splitting is clearly resolved. The observations were fitted to an effective Hamiltonian model and values of the magnetic hyperfine parameters of b F = −0.0302 cm −1 for the A state and d = 0.0024 cm −1 for the X state were determined. An interpretation of these values in terms of the proposed electronic configurations of these states is presented.

Spin dynamics in a 3d Heisenberg ferromagnet in the paramagnetic state. I

A description of the nuclear spin lattice relaxation in insulating Heisenberg magnets is outlined. Nuclear spin lattice relaxation times are expressed in spectral densities φ α ij (ω) using measured nuclear magnetic hyperfine and electric quadrupolar interaction parameters. Experimentally the relaxation behaviour of some nuclei ( 87Rb, 79Br, 1H) in Rb 2CuBr 4 · 2H 2O has been studied using spin echo techniques. It is shown that by comparing the T 1 data from different nuclei reliable absolute values for the auto-and pair correlations can be obtained. The detailed presentation and discussion of these results will be given in part II.

NMR-ON of182Ta and183Ta in Fe

Nuclear magnetic resonance has been observed on radioactive182Ta and183Ta oriented at low temperature in an Fe host, by detection of the change in spatial anisotropy of γ-rays emitted during nuclear decay. By measuring the resonant frequencies of183Ta in four different applied magnetic fields the nuclear magnetic moment and hyperfine field have been deduced. These are: $$|\mu \left( {{}^{183}Ta; I = \tfrac{\user2{7}}{\user2{2}}} \right)| = 2.28(3)\mu _{\rm N} and B_{hf} \left( {Ta\underline {Fe} at 0 K} \right) = - 67.2(1.3)T$$ . The spin of the ground state of182Ta has been determined asI=3 by comparing resonance results with those obtained in a thermal equilibrium nuclear orientation study. The ratio of the resonant frequencies observed for182Ta and183Ta at one applied field value yields a magnetic moment for the former of $$|\mu \left( {{}^{182}Ta; I = \user2{3}} \right)| = 2.91(3)\mu _{\rm N} $$ . The spin lattice relaxation time for183TaFe (0.12 at% Ta) at 18 mK in an applied field of 0.5 T has been found to be 40(10) s.

NMR-on of182Ta and183Ta in Fe

Nuclear magnetic resonance has been observed on radioactive182Ta and183Ta oriented at low temperature in an Fe host, by detection of the change in spatial anisotropy of γ-rays emitted during nuclear decay. By measuring the resonant frequencies of183Ta in four different applied magnetic fields the nuclear magnetic moment and hyperfine field have been deduced. These are: $$|\mu \left( {{}^{183}Ta; I = \tfrac{\user2{7}}{\user2{2}}} \right)| = 2.28(3)\mu _{\rm N} and B_{hf} \left( {Ta\underline {Fe} at 0 K} \right) = - 67.2(1.3)T$$ . The spin of the ground state of182Ta has been determined asI=3 by comparing resonance results with those obtained in a thermal equilibrium nuclear orientation study. The ratio of the resonant frequencies observed for182Ta and183Ta at one applied field value yields a magnetic moment for the former of $$|\mu \left( {{}^{182}Ta; I = \user2{3}} \right)| = 2.91(3)\mu _{\rm N} $$ . The spin lattice relaxation time for183TaFe (0.12 at% Ta) at 18 mK in an applied field of 0.5 T has been found to be 40(10) s.

Proton nuclear magnetic resonance hyperfine shifts as indicators of tertiary structural changes accompanying the Bohr effect in monomeric insect hemoglobins.

Proton nuclear magnetic resonance hyperfine shifts as indicators of tertiary structural changes accompanying the Bohr effect in monomeric insect hemoglobins.

Hyperfine structure in the electronic spectrum of 127I2 by saturated absorption spectroscopy at 633 nm

The full hyperfine components of the R (127) line in the 11-5 band and the 10 components of the P (33) line in the 6-3 band of the B←X electronic transition of 127I2 were observed by the saturated absorption spectroscopy using a complex resonator He-Ne laser. The frequency of the laser was locked to each component and the frequency separations of the components were precisely measured. The hyperfine structure of the R (127) line was compared with a model which included both a nuclear electric quadrupole and magnetic hyperfine interactions.

ENDOR spectra for155Gd3+in ThO2

The nuclear magnetic moment (uncorrected for diamagnetic shielding) and hyperfine structure parameters of 155Gd3+ in ThO2 have been obtained from ENDOR measurements performed at 35 GHz. The complete angular dependence of the ENDOR spectra can be explained by including a fourth-rank mixed tensor operator of second order in electronic and nuclear spin variables. Tetragonal stress-induced nuclear quadrupolar splittings were also observed and good agreement with estimates based on a point-charge model was obtained.

The Electronic Spectrum of Gaseous AIF

The results of a detailed rotational analysis involving the assignment of some 14 500 lines are reported. Observed bands have been ascribed to transitions between nine singlet states (including the ground state) and between seven triplet states. Singlet-triplet systems have not yet been observed, but the relative energies of the singlet and triplet states have been determined by the analysis of spin-forbidden perturbations. The ground state is π4σ2, X1Σ+, and the first excited states π4σπ*, a3Πr, A1Π. Above these lie two further non-Rydberg states, B1Σ+ and b3Σ+, which seem to arise from a configuration of the kind π4σσ*. The remaining eleven states seem to be Rydberg states, π4σ(nlλ) 3Λ, 1Λ, which converge on the 2Σ+ ground state of AlF+. However, no series have yet been recognized so that neither is the ionization potential of AlF well determined nor are there certain assignments of the Rydberg states, although suggestions are made. The triplet splittings in all but the a3Π state are very small (and in some systems there may be cancellation), so that the 3Σ+-3Σ+ transitions and a 3Π-3Σ+ system simulate, even at fairly high resolution, 1Σ-1Σ and 1Π-1Σ systems respectively. At high resolution lines of the 3Σ+-a3Π systems show small splittings, some of which are of the kind expected for nuclear magnetic hyperfine structure in transitions of the type case (bβ-S)-case (aβ); however some of the observations are not yet understood.

Nuclear shielding and magnetic hyperfine structure of hydrogen cyanide

A millimeter-wave molecular beam maser has been used to resolve the magnetic hyperfine structure of hydrogen cyanide. The spin-rotation interaction constants have been measured for the three nuclei 14N, 13C, and H. The paramagnetic nuclear shielding factors have been calculated for the three nuclear sites. The spin-rotation constants for 14N in H 12C 14N, for H in H 12C 14N and for 13C in D 13C 14N are + 10.4 kHz, −3.7 kHz, and +15.0 kHz, respectively. The respective paramagnetic shielding factors are −408.98 × 10 −6, −73.40 × 10 −6, and −249.52 × 10 −6.

Raman active lattice spectrum of single crystal 2,4,6-triphenyltriazine

Crystals of hydrated europium bromate were grown and magnetic susceptibilities measured from room down to liquid oxygen temperatures. The effective magnetic moment peff is found todecrease with decreasing temperature indicating a Van Vleck high temperature contribution. The magnetic anisotropy Δχ=χ‖−χ⊥ is negative and appreciable. The magnetic susceptibilities χ‖; and χ⊥ parallel and perpendicular to c-axis, respectively, rise slowly with decreasing temperature, and around 115 K χ⊥ becomes nearly constant while χ‖ decrease slightly; this is quite in contrast to the behavior of other rare earth bromates. A crystal field conforming to D3h symmetry provided a satisfactory explanation to the observed magnetic behavior. The crystal field parameters used are B20=175, B40=−304, B60=−864 and B66=910 all in cm−1. The Schottky heat capacity Cs does not display any anomaly and vanishes below 50 K. Nuclear quadrupole and magnetic hyperfine splitting due to the crystal field has been worked out. The hyperfine heat capacity for both isotopes shows Schottky anomaly below 2 mK.

A pseudopotential based theory of the driving forces for electromigration in metals

Crystals of hydrated europium bromate were grown and magnetic susceptibilities measured from room down to liquid oxygen temperatures. The effective magnetic moment peff is found todecrease with decreasing temperature indicating a Van Vleck high temperature contribution. The magnetic anisotropy Δχ=χ‖−χ⊥ is negative and appreciable. The magnetic susceptibilities χ‖; and χ⊥ parallel and perpendicular to c-axis, respectively, rise slowly with decreasing temperature, and around 115 K χ⊥ becomes nearly constant while χ‖ decrease slightly; this is quite in contrast to the behavior of other rare earth bromates. A crystal field conforming to D3h symmetry provided a satisfactory explanation to the observed magnetic behavior. The crystal field parameters used are B20=175, B40=−304, B60=−864 and B66=910 all in cm−1. The Schottky heat capacity Cs does not display any anomaly and vanishes below 50 K. Nuclear quadrupole and magnetic hyperfine splitting due to the crystal field has been worked out. The hyperfine heat capacity for both isotopes shows Schottky anomaly below 2 mK.

Analysis of the transition B2Σ+-X2Σ+in gaseous LaS

Bands of gaseous LaS have been observed in thermal emission and in absorption, and the vibrational analysis of one system B2 Sigma -X2 Sigma + in the region 7000 to 8500 AA has been obtained, together with the rotational analysis of the 0-0 band. The bands possess four R and Four P branches, and the splittings can be interpreted in terms of (i) a large spin splitting gamma (N+1) in the upper state, (ii) a J independent case bbeta s nuclear magnetic hyperfine interaction in the ground state whose magnitude is within experimental error the same as in LaO.