Numerical solutions for single passage NMR on nuclei experiencing small electric quadrupole interactions

The adiabatic rapid-passage NMR equations are numerically solved for a small additional quadrupole interaction. The full range of the ratio of rf interaction strengths to quadrupole interactions strengths is considered for any electric field gradient orientation. The results forI=1 are particularly easy to describe and are used to predict the single-passage results for different orientations of the electric field gradient with respect to the static magnetic field.     

The extraction of weak nuclear electric quadrupole splittings of dilute impurities in ferromagnets using modulated Adiabatic Passage NMR/ON

A novel extension of the Single or Adiabatic Fast Passage NMR/ON technique is described. Its principal advantages in extracting the mode magnitudes and distribution widths of weak nuclear electric quadrupole splittings much less than the magnetic inhomogeneous broadening are its simplicity and generality requiring no assumptions on the degree of adiabaticity of the nuclear spin motion during sweep through the quadrupolar split subresonances. The technique is applied to a concentrated single crystal sample of⁶⁰CoFe which failed to yield a well resolved mid passage signal to conventional single passage NMR/ON. The result is an asymmetric frequency distribution of quadrupole frequencies with a mode value of P=3e²qQ/4I (2I-1)=+4.5 ±1.0 kHz and half maxima of +2.5 kHz and +7.0 kHz.     

Static electric quadrupole and hexadecapole moments of nuclei

Ground-state static electric quadrupole and hexadecapole moments of even nuclei are calculated microscopically. Rare-earth, actinide and neutron-deficient nuclei with 50 <Z, N < 82 and neutron-rich nuclei with 28 < Z < 50, 50 < N < 82 are studied. Fairly good agreement with experiment is found. In the actinide region, the electric moments of fission isomers are also examined.     

Current electric quadrupole moments of atoms and nuclei

It is shown that current electric multipoles exist. Their field is electrostatic and it is unrelated to the existence of a net electric charge. At long range, it is the same as the field of the corresponding charge electric multipoles. Current electric multipoles arise during the motion of magnetic multipoles. An orbital motion of magnetic dipoles, a precession of a current-carrying loop, and the motion of magnetic quadrupoles all lead to current electric quadrupole moments. Expressions for the current electric quadrupole moments of atoms and nuclei are derived.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 53–58, July, 1991.The author wishes to thank S. A. Kuten' and V. I. Rapoport for useful comments offered during the writing of this paper and for a discussion of the results.     

Fundamental weak interaction studies using polarised nuclei and ion traps

Two experiments to search for new physics beyond the standard model for electroweak interactions by measuring correlations between different spin and momentum vectors in nuclear β-decay are discussed. In the first experiment the correlation between the emission asymmetry and the longitudinal polarisation of positrons emitted by polarised nuclei is determined. This type of measurement is sensitive to the presence of right-handed currents but also to possible scalar and tensor-type currents in the weak interaction. The aim of the second experiment is to determine the βν-correlation in β-decay by measuring the energy spectrum of the recoil ions, using a Penning trap and a retardation spectrometer. In this case the focus is on the search for scalar currents in the weak interaction. The results of the experiments presented here are complementary to results from experiments in muon decay and at high-energy colliders. This revised version was published online in July 2006 with corrections to the Cover Date.     

Electric quadrupole interactions measured by nuclear orientation and NMR on oriented nuclei

A review is given of the situations in which low temperature nuclear orientation and NMR of oriented nuclei have been applied in recent years to the measurement of electric quadrupole interactions in metals and in dielectric crystals. The review is concerned with the variety of methods by which quadrupole interactions have been measured. Illustrative examples are given for each technique, but no attempt is made to give a full bibliography of work. As regards nuclear orientation, pure quadrupole algnment is discussed (although in non-cubic metals rather than in dielectric crystals), followed by outlines of work on mixed magnetic dipole and electric quadrupole hfi when these interactions are (a) co-axial and (b) mutually perpendicular. The sensitivity of nuclear orientation to small quadrupole interactions is shown to be improved in the second case.For NMR on oriented nuclei the review centres upon the small quadrupole effects detected in dilute ferromagnetic alloys both by direct observation of resonance line structure and by interpretation of signals following adiabatic fast passage.Republished from the XVIIth Winter School on Physics (Hyperfine Interactions) held from February 19-March 3, 1979 in Bielsko Biala (Poland), with the kind permission of the Editors.     

Coherent adiabatic passage in atomic systems with a closed interaction contour

The effectiveness of coherent adiabatic passage in atomic systems with a closed interaction contour was studied. The dependence of coherent adiabatic passage on the algebraic sum of initial exciting field phases was demonstrated for the example of a double Λ-system of atomic levels. The conditions that should be met by interaction parameters for the occurrence of effective coherent adiabatic passage at various atomic contour phases were determined.     

Nuclear electric quadrupole interaction of implanted ions in graphite

A number of isotopes have been implanted into thin foils of highly oriented pyrolytic graphite in order to investigate the possibility of using this material as a catcher for on-line LT-NO experiments to measure the quadrupole interaction of short-lived nuclei. Pure nuclear electric quadrupole interaction of nuclei of^188,189Ir,²⁰³Hg,^69mZn,^182m,183Re and¹¹¹In has been observed. Values for the electric field gradient along theC-axis are: +10.0(3) +8.2(9), +5.4(2.6) and +1.5(1)·10²² V/m², respectively, for Ir, Hg, Re and In in graphite. A value ofQ=+0.79(6) b is deduced for the quadrupole moment of¹⁸⁹Ir. Two theoretical models provide a better understanding of the origin of the electric field gradient in graphite. The first is based on induced electric polarization of graphite atoms, while in the second one hybridization of impurity and graphite electronic wave functions is calculated.     

Precision measurement of the electric quadrupole interaction in zinc metal

To decide on the validity of various values for the quadrupole coupling constant of Zn metal available in the literature, we have used the frequency modulation technique to the 93.3 keV Mössbauer resonance of⁶⁷Zn. We obtained for a⁶⁷Zn metal absorber: e²qQ/h =v _O = 12.34 ± 0.03 MHz. The asymmetry parameter was found to be =0.00 _–0 ^+0.06 . These precise values can be used as a calibration standard for⁶⁷Zn Doppler drives.This work has been supported by the Bundesministerium für Forschung und Technologie and by the Kernforschungszentrum Karlsruhe.     

The interaction and fusion of arbitrarily oriented deformed nuclei

The fusion/capture cross sections between various deformed nuclei are calculated. It is shown that quadrupole and hexadecapole deformations of heavy nuclei are important for evaluating the barrier height, capture well depth, and fusion/capture cross sections of heavy nuclei. It is found that calculations of the capture cross section of two heavy deformed nuclei must be performed with averaging over all possible mutual orientations of the colliding nuclei.     

Do we understand the electric quadrupole strength distributions in magic nuclei?

A comparison between the electric quadrupole (E2) strength distributions in ^{40, 48}Ca with new results from ⁵²Cr is presented. The deduced E2 strength distributions and the exhaustion of the isoscalar energy-weighted E2 sum rule are very different. Microscopic approaches fail to reproduce these differences. A survey of the available data shows that the exhaustion of the energy-weighted isoscalar E2 sum rule in doubly magic nuclei below the isoscalar giant quadrupole resonance is typically more than two times larger than in semi-magic nuclei. On the other hand, the E2 strength in this energy region exhausts about 50% of the total E2 strength, independent from shell closures.     

A method for calculating adiabatic mass parameters: Application to isoscalar quadrupole modes in light nuclei

A method is given which reduces the evaluation of adiabatic inertial parameters to constrained Hartree-Fock calculations. Quadrupole masses are computed for some light nuclei. As a result of dynamical effects ¹²C is found to become oblate.     

On the effect of quadrupole pairing interaction on the backbending behaviour in rotating nuclei

The influence of the quadrupole component in the nucleon-nucleon pairing foce on the rotational nuclear motion is investigated with a simple model in connection with the backbending phenomenon. The inclusion of this component although necessary in the realistic calculation does not affect considerably the qualitative picture of the phenomenon.     

Structural phase transition in cadmium titanate observed by electric quadrupole interaction

The quadrupole interaction at¹¹¹Cd nuclei was measured in the ferroelectric perovskite CdTiO₃ at different temperatures using the PAC method. The interaction parameters indicate a structural phase transition around 50 K.     

NMR-ON measurement of the electric quadrupole interaction of199Au in Fe

The magnetic-dipole and electric-quadrupole interaction frequencies of¹⁹⁹AuJ ^π=3/2⁺ T _1/2=3.1 d) in Fe were measured with nuclear magnetic resonance on oriented nuclei as 166.69(4) MHz and ?1.52(2) MHz, respectively. This quadrupole splitting is in disagreement to the value previously reported.     

Temperature dependence of electric quadrupole interaction of181Ta in HfO2

High-resolution TDPAC determination of EQI of¹⁸¹Ta in HfO₂ is performed. Room temperature parameters of ω_Q = 111 (1) MHz and η=0.36(1) are obtained. The temperature dependence of ω_Q and η in the range 78–1100 K is established. An explanation of the observed phenomena in a dielectric lattice is discussed.