Nuclear Magnetic Dipole Moments Research Articles

Nuclear deformation of holmium isotopes

Hyperfine structures and isotope shifts of holmium isotopes and isomers in the mass range 152–165 have been measured for the atomic transition of 592.17 nm using resonance ionization Spectroscopy. Nuclear magnetic dipole and electric quadrupole moments, and changes in mean square charge radii have been derived from the results. Nuclear spins for some isotopes and isomers have been determined too. A sudden change of nuclear deformation between N = 89 and N = 90 has been found. The experimental data are discussed within the framework of the macroscopic-microscopic approach and the Hartree-Fock method. The intrinsic quadrupole moments, including their change at N = 89–90, are described fairly well. At the same time, some difficulties in the description of the mean square charge radii by the Hartree-Fock theory have been revealed.

Quark deconfinement in nuclei: A review of experimental tests based on nuclear magnetic moment measurements

The introduction very briefly outlines the basic idea and experimental evidence to suggest that quarks may behave differently in nuclei and in indididual nucleons, with possible consequences for the calculation of nuclear magnetic dipole moments. After description of a calculation of moments made using the extreme model of total quark deconfinement (the MIT bag model) attention is focussed on experimental tests and the state of current evidence for more partial quark deconfinement. The arguments of Yamazaki which give an experimental basis for distinguishing quark deconfinement effects from, specifically, effects caused by pion echange currents, are given in more detail. The reasons underlying choice of nuclei in which meaningful tests may be possible are given. Early claims by Karl et al. to have demonstrated the existence of quark deconfinement in mass 3 nuclei are discussed. The current status of evidence for deconfinement based on orbital gfactor measurements in heavier nuclei is also summarised. Finally some examples are given of possible experiments using recently developed on-line facilities which may provide further tests of these ideas.

The sign of the magnetic dipole moment of the ground state of122I

The sign of the nuclear magnetic dipole moment of the ground state of122I has been determined to be positive using a novel experimental technique. The technique investigates the asymmetry of positron emission by detecting the 511 keV gamma-rays produced on the annihilation of the positrons. The method would appear to have general validity for studying the sign of the magnetic moment in other cases where theβ+ decay is relatively simple.

Étude structurale de l'amino-5 dibenzyl-4,4 one-3 2H-thiadiazine-1,2,6 dioxyde-1,1

5-Amino-4,4-dibenzyl-3-one-2H-1,2,6-thiadiazine-1,1-dioxide was structurally characterized in the solid state by X-ray diffraction. The structure shows that the title compound exists in the solid in a sheet-packed form and as the amino tautomer. The unconjugated heterocyclic ring, which in the structures of related compounds is usually folded, is planar in the present structure. 1H nuclear magnetic resonance and dipole moment data indicate that the title compound has the same structure in the solid state and in solution.

Nuclear electromagnetic moments and charge radii of deformed thulium isotopes with the mass numbers A = 157−172

Hyperfine structures and isotope shifts of thulium isotopes in the mass range 157–172 have been measured in the atomic transitions 4f 136s 2−4f 125d6s 2 (589.565 nm) and 6s 2−6s6p (597.13 nm), using resonance ionization Spectroscopy at the IRIS facility. Nuclear magnetic dipole and electric quadrupole moments, and the changes in mean square charge radii have been obtained. They are analysed within the framework of the microscopic-macroscopic approach and the Hartree-Fock method, revealing single-particle and collective properties. Some conclusions on effective nucleon-nucleon interactions are drawn.

Nuclear Properties by Laser Spectroscopy in Beams and Rings

Laser spectroscopy is discussed as a source of information about nuclear physics properties. The quantities measured in such an experiment are atomic physics properties, namely the isotope shift and the hyperfine structure of the optical fluorescence spectra in the visible wavelength band. Nuclear physics information describing properties of the ground state and isomeric states of a nucleus can be extracted from these data, namely nuclear magnetic dipole moments, nuclear electric quadrupole moments, nuclear spins and the changes of the mean square charge radii between isotopes. Some recent results are reported as examples. The method of collinear fast-atomic-beam spectroscopy using the isotopically pure beams of on-line mass-separators and a very similar technique which has been proposed to study the hyperfine structure of hydrogen-like ions in the storage ring for cooled ions, ESR, under construction at GSI, are discussed.

HFS and isotope shift in the atomic spectrum of205Pb

The hfs of205Pb in the 283.3-nm resonance line and its isotope shift (IS) have been measured in absorption with the use of dispersive spectroscopy. A new method for calibration and analysis, when internal standards are not available is described. The results are: hfs interaction constantsA=70.3(5)×10−3 cm−1,B=−0.6(1.1)×10−3 cm−1,205Pb-208Pb IS=−123.9(2.0)×10−3 cm−1. The derived nuclear magnetic dipole moment,μ=0.704(5)μ N is in good agreement with values calculated with a nuclear configuration mixing model.

Spins, moments and mean square charge radii of 104–127In determined by laser spectroscopy

Hyperfine structures and isotope shifts of indium isotopes in the mass range 104–127 have been measured in the atomic transitions 5 p 2 P 1 2 -6 s 2 S 1 2 (410 nm) and 5 p 2 P 3 2 -6 s 2 S 1 2 (451 nm) by collinear fast-beam laser spectroscopy. Nuclear magnetic dipole and electric quadrupole moments have been determined for 37 ground and isomeric states. The magnetic moments in the sequence of the 1 2 − isomers are found to cross the Schmidt limit. Magnetic dipole and electric quadrupole moments of the odd-odd isotopes are compared to values obtained by additivity rules. The 8 − isomers exhibit a strong change in the coupling of the h 11 2 neutrons to the collective motion. The mean square charge radii show a parabolic behavior with a maximum in the middle of the neutron shell at N = 66. This is interpreted by collective effects, which are considerably stronger than seen in the quadrupole moments or in the B(E2) values of neighbouring doubly-even nuclides.

Nuclear magnetic relaxation for coupled spins of oppositely signed magnetic moments

The frequency dependence of various relaxation parameters for a two-spin system composed of nuclei with oppositely signed magnetic moments and relaxed by intramolecular dipolar interactions is described. It is demonstrated that significant discrepancies exist between theories that explicitly consider or implicitly ignore relative signs of the nuclear magnetic dipole moment.

Nuclear and Electronic g-Factors of 211Fr, Nuclear Ground-State Spin of 207Fr and the Nuclear Single-Particle Structure in the Range 207-228Fr

The nuclear and electronic magnetic dipole moments of 21Fr and the nuclear ground-state spin of 207Fr have been measured directly by on-line atomic-beam magnetic resonance techniques at the ISOLDE facility at CERN. The following results have been obtained: μI(211Fr) = 4.00(8) nm, gJ(Fr, 7s 2S1/2) = 2.00497(9) and I(207Fr) = 9/2. A large deviation of the electronic magnetic moment from the free electron value was found. Using the measured nuclear magnetic moment μI(211Fr), a comparison is made between different theoretical calculations of the magnetic dipole hyperfine constants and with the available experimental data in 211Fr. An analysis of the electric quadrupole interaction is also given. Nuclear magnetic dipole and electric quadrupole moments are deduced for the sequences 207-213Fr and 220-228Fr, using the data on 211Fr as reference values. The nuclear quantities are discussed within the framework of the shell model and the core-quasiparticle model, giving information on the nuclear single-particle structure and on the variation in deformation along the sequences of francium isotopes.

Chemical shift imaging: a review.

Chemical shift is the phenomenon that is seen when an isotope possessing a nuclear magnetic dipole moment resonates at a spectrum of resonance frequencies in a given magnetic field. These resonance frequencies, or chemical shifts, depend on the chemical environments of particular nuclei. Mapping the spatial distribution of nuclei associated with a particular chemical shift (e.g., hydrogen nuclei associated with water molecules or with lipid groups) is called chemical shift imaging. Several techniques of proton chemical shift imaging that have been applied in vivo are presented, and their clinical findings are reported and summarized. Acquiring high-resolution spectra for large numbers of volume elements in two or three dimensions may be prohibitive because of time constraints, but other methods of imaging lipid of water distributions (i.e., selective excitation, selective saturation, or variations in conventional magnetic resonance imaging pulse sequences) can provide chemical shift information. These techniques require less time, but they lack spectral information. Since fat deposition seen by chemical shift imaging may not be demonstrated by conventional magnetic resonance imaging, certain applications of chemical shift imaging, such as in the determination of fatty liver disease, have greater diagnostic utility than conventional magnetic resonance imaging. Furthermore, edge artifacts caused by chemical shift effects can be eliminated by certain selective methods of data acquisition employed in chemical shift imaging.

Refined models for computer calculations in protein engineering: Calibration and testing of atomic potential functions compatible with more efficient calculations

A reappraisal has been made of interatomic potential functions for protein structure calculations using the all-atom approximation (except CH, CH 2 and CH 3, which are treated as “united atoms”). Some key problems are identified and treated. The potential functions are somewhat novel in form and consistent with more efficient and robust folding algorithms. In addition, the potentials are calibrated for the rigid geometry approximation, since use of fixed standard bond lengths and valence angles (and fixed trans planar peptide groups) reduces the number of conformational variables and saves a great deal of computer time. Though these algorithms demand the use of potential functions of this special type, these functions can be readily implemented in more classical programs for the conformational analysis of proteins. They are calibrated or tested against a large body of experimental data, including (1) extended basis set ab initio, quantum mechanical calculations, (2) nuclear magnetic resonance spectroscopic data and dipole moment data for di- and oligopeptides, (3) characteristic ratio data for random coil homopolypeptides, (4) extensive data from peptide solubility studies, and (5) experimental structures of polyalanine fibres and globular proteins. This paper will form the basis of a further report, which will include investigations of how water might be more realistically represented subject to the computing power available.

Nuclear moments of the low abundant natural isotope 176Lu and hyperfine anomalies in the lutetium isotopes

Abstract The atomic beam magnetic resonance method combined with laser-induced state- and isotopeselective detection of metastable atoms has been used to investigate the hyperfine structure of the 2D ground multiplet in 175Lu and 176Lu. The analysis of the data yields not only accurate values for the hyperfine interaction constants, the nuclear magnetic dipole moment of 175Lu, and the electronic gJ, factors, but also the first directly measured value of the nuclear magnetic dipole moment of the low abundant isotope 176 Lu : μ I ( 176 Lu) = 3.1692 (45)μ N (corrected for diamagnetic shielding). The spectroscopic quadrupole moment of 176Lu was calculated from the ratio of the B-factors and the quadrupole moment of 175 Lu : Q s ( 176 Lu ) = 4.92 (3) b . Moreover, the magnetic hyperfine anomalies for the isotopic chain 175,176,176m,177Lu were determined. A quadrupole hyperfine anomaly between 175Lu and 176Lu was not found when comparing the ratio of the B-factors in the states 2 D 3 2 and 2 D 5 2 . From a comparison of the quadrupole moment of 175Lu obtained from the hyperfine structure data and the quadrupole moment measured in muonic lutetium atoms semi-empirical Sternheimer shielding factors could be estimated.

Direct measurement of the nuclear magnetic dipole moments of 191Ir and 193Ir by high-precision atomic beam magnetic resonance

For the four lowest atomic levels of 191Ir and six levels of 193Ir the hyperfine structure constants A, B, and C were determined by high-precision atomic beam magnetic resonance. Using the triple-resonance technique, ΔM J =0, ΔM I =1 transitions, which depend strongly on the nuclear g I factors, were investigated at magnetic fields up to 2100 Oe, and the following values for the nuclear magnetic dipole moments were deduced: μ I( 191 Ir)=0.1485(6)μ N , μ I( 193 Ir)=0.1613(6)μ N (uncorrected for atomic diamagnetism).

Determination of nuclear spins and moments in a series of radium isotopes

The first investigation of hyperfine structure in radium isotopes has enabled the determination of nuclear spins, magnetic dipole and electric quadrupole moments of the isotopes with mass numbers A = 211, 213, 221, 223, 225, 227 and 229. Isotope shifts in the mass range A = 208−232 have also been measured. These studies were carried out using the technique of on-line collinear fast beam laser spectroscopy.

Spins, moments and charge radii of barium isotopes in the range 122–146Ba determined by collinear fast-beam laser spectroscopy

Hyperfine structures and isotope shifts of barium isotopes in the mass range 122–146 have been measured in the atomic transition 6 s 2 1 S 0→6 s6 p 1 P 1 (5536 A ̊ ) , utilizing collinear fast-beam laser spectroscopy at the ISOLDE facility at CERN. Nuclear spins, magnetic dipole and electric quadrupole moments, and the changes of mean square charge radii have been deduced. They are discussed within the framework of current nuclear models, revealing single-particle structure and nuclear-shape variations on both sides of the N = 82 neutron-shell closure.

High-resolution measurements of isotope shifts and hyperfine structure in stable and radioactive lead isotopes

The authors present new measurements of isotopic shifts and hyperfine structure in the lead resonance line for a total of 15 isotopes. The experimental accuracy is of order 4 MHz. Using independent measurements of the nuclear parameter lambda for the stable isotopes they have derived lambda for all measured isotopes. The derived values of lambda are compared with various theoretical predictions for the lead nuclei. The authors also give values for the nuclear magnetic dipole and electric quadrupole moments deduced from the measurements.

Measurement of the magnetic moment of the 7 + isomer in 198Tl

Using the atomic beam magnetic resonance method the hyperfine structure separation of 1.9 h 198m Tl (I π = 7 +) has been measured in the 2 P 1 2 atomic ground state. From the hyperfine structure splitting the nuclear magnetic dipole moment has been deduced. The results are: Δν = 4500 (68) MHz, μ I = 0.641(10) μ N. This is an improvement of approximately one order of magnitude compared to a previous measurement. The quoted value of the magnetic dipole moment includes corrections for the hyperfine structure anomaly and for diamagnetic shielding.

The nuclear magnetic moment of186Ir

The nuclear magnetic dipole moment of 186Ir has been deduced from a study of the gamma rays emitted by 186Ir oriented at low temperature in an iron host. The deduced value of 3.88(5) mu N compares favourably with recent NO/NMR results. The measured magnetic dipole and electric quadrupole moments are shown to be consistent with values calculated assuming the spin-5 186Ir to be a mixture of K=0 and K=1, with the interference term between the two components contributing about half the value of the magnetic moment. Multipole mixing ratios of 186Os gamma rays are deduced and compared with results of band-mixing calculations.

Hyperfine structure investigations in Sm II by collinear laser spectroscopy and nuclear moments of151Sm

We have measured the hfs of the Sm II linesλλ=656.9 nm and 657.1 nm by collinear laser spectroscopy. From the a-and b-values the ratios of nuclear magnetic dipole and electric quadrupole moments are derived. For151Sm we obtain μ(151)=−0.3622(5) μn and Q(151)=0.52 (5) b.