Low temperature nuclear orientation of239Np in gadolinium host

The angular distribution of γ-radiation from the decay of²³⁹Np oriented at low temperatures in gadolinium host was investigated. The orientation parameters B2 and B4 were determined. The attenuation factors for two long-living states in²³⁹Pu at 391.5 keV and 285.4 keV were calculated. From the anisotropies measured the multipole mixing ratios for 11 gamma-transitions in²³⁹Pu were deduced. The results obtained support the assignment of spins of the levels at 492.2 keV and 391.6 keV as 3/2⁻ and 7/2⁻, respectively.     

Low temperature nuclear orientation of238NpGd

The decay of²³⁸Np oriented at low temperatures in gadolinium host was investigated. Multipole mixing ratios for beta-transition to the level 1028.6 keV and nine gamma-transitions in²³⁸Pu were calculated from the anisotropies of gamma radiation. The attenuation factor for the isomeric state of²³⁸Pu at 1082.6 KeV and orientation parameters for²³⁸NpGd were deduced from the experimental results.     

Low temperature nuclear orientation of a dilute RhCr alloy

A dilute^101mRhCr alloy has been investigated by means of low temperature nuclear orientation in the temperature range of 6–60 mK. The magnetic hyperfine field has been found proportional to the macroscopic chromium magnetization and follows even at these low temperatures an Overhauser distribution. The maximum hyperfine field value is B_o (T=6 mK)=7.0(5) T. A Knight shift of –16% affects the external magnetic field at the nuclear site.     

Low temperature nuclear orientation and NMR of oriented nuclei

Recent developments in nuclear orientation (NO) and radiative detection of NMR (NMR/ON) are reviewed. Details of the hyperfine interaction hamiltonian in cubic ferromagnets and the principles of measurement by these techniques of both magnetic dipole and electric quadrupole terms are outlined. In the experimental survey a full account is given of measurements of the electric quadrupole interaction by frequency modulated and fast passage NMR/ON, with briefer coverage of applications of both techniques to implanted systems, of linewidths, concentration dependent line structure, and Knight shifts in NMR/ON and of NO measurements of electric quadrupole interactions in non-cubic non-magnetic metals. The review incorporates a tabulation of NMR/ON measurements to date.     

Low temperature nuclear orientation and its application to magnetic systems

This article contains an outline of the basic principles of low temperature nuclear orientation LTNO and of nuclear magnetic resonance on oriented nuclei NMR/ON. A summary is given of the experimental requirements and constraints of these methods followed by a survey of their applications to the study of magnetism in solids. More detailed consideration is given to relaxation topics, including fast passage and pulsed RF techniques, and to the variety of methods now available, based on nuclear orientation and resonance, for the separate extraction of magnetic dipole and electric quadrupole interaction strengths when they occur together.     

Low-spin states in151Gd

The level structure of the 87-neutron nucleus¹⁵¹Gd has been investigated by studying the EC- andβ ⁺-decay of¹⁵¹Tb. Gamma-ray and conversion electron spectra as well as gamma-gamma coincidence spectra were measured by using semiconductor spectrometers and a high-capacity two-parameter recording system. The proposed decay scheme contains several new energy levels in¹⁵¹Gd, among them a 5^?/2 state at 427 keV. To explain the low-energy level structure, a small stable deformation is assumed for¹⁵¹Gd. Using a single-particle-plus-rotor model based on a generalized Woods-Saxon potential, complete mixing of the shells 1h _9/2, 2f _7/2 and separately 1i _13/2 is observed. By these mixings the correct level order and approximately correct excitation energies up to 1 MeV are reproduced.     

Applications of low temperature nuclear orientation

The techniques of low temperature nuclear orientation (LTNO) and nuclear magnetic resonance on oriented nuclei (NMRON) are versatile tools used across a range of applications. Such applications include nuclear moment and hyperfine field measurements and testing of nuclear decay models, as well as condensed matter studies, particularly applied to magnetism. Following the tradition of such presentations, the techniques LTNO and NMRON, are briefly outlined along with the principal applications with a focus on some recent works.     

New directions in low temperature nuclear orientation

The basis of the low temperature nuclear orientation technique is summarized. The present limitations on accessible temperatures and the orders of magnitude of hyperfine interactions in the metallic systems currently studied are discussed briefly. The broad applicability to many elements and the high sensitivity of this singles counting method are emphasized. Specific recent developments are discussed in more detail. The use of a dilution refrigerator to cool to ≈ 10mK nuclei of isotopes far from stability ‘on-line’, after production in an accelerator and electromagnetic selection, is a major extension of the method. The minimum half-life is now limited by the nuclear spinlattice relaxation time, typically of order 10–100 s at 10 mK. Aspects of these experiments are considered and recent results given for Cs and I isotopes. Secondly, the extension of the related technique of nuclear magnetic resonance or oriented nuclei (NMR/ON) to antiferromagnetic insulators is described. A new cooling mechanism involving nuclear-magnon coupling gives access to much lower temperatures than previously reached in these systems. Recent precision work on MnCl₂, 4H₂O is discussed, along with its possible extension to nuclei of lanthanide elements. Finally, the use of nuclear orientation to study ordering below 10 mK of enhanced nuclear moment systems is briefly surveyed, with HoVO₄ as the test case. NMR/ON experiments at high pressure are proposed.     

Low temperature nuclear orientation studies of the magnetic structures of RNiAl4 in applied magnetic fields

The accumulation of iron and arsenic from aqueous solution by lettuce leaves biomass was investigated using Mössbauer and EXAFS spectroscopic techniques. Mössbauer spectroscopy results show that iron is oxidized during sorption while EXAFS results indicate that iron is coordinated by approximately 6 oxygen and 2 carbon atoms while arsenic is coordinated by approximately 4 oxygen atoms with iron as a second neighbor.     

Decay of149Gd and directional correlations of gamma cascades in149Eu

The decay of¹⁴⁹Gd(9.4d) to the levels of¹⁴⁹Eu has been studied using large volume high resolution Ge(Li) and NaI(Tl) detectors,γ-γ coincidence and directional correlation experiments have been performed. Newγ-rays at energies 131.9, 278.6, 384.7, 415.7, 599.2, 726.5, 734.7, 956.4 and 1,231.1 keV in¹⁴⁹Eu have been observed. Three new levels in¹⁴⁹Eu have been placed at 956.4, 1,082.0 and 1,231.1 keV. Spin-parity assignments have been made to some of the levels in¹⁴⁹Eu. Multipolarity assignments have been made for most of the electromagnetic transitions from the conversion coefficients obtained through the knowledge of ourγ-transition intensities and the published conversion-electron intensities. Based on the newγ-transitions observed in the singles and coincidence spectra, a revised level scheme has been proposed for¹⁴⁹Eu and compared with previously published level schemes. Radioactivity¹⁴⁹Gd; measuredT _1/2,T _γ,γγ coin, γγ(θ), I.C.C.,¹⁴⁹Eu deduced levels,J,γ-mixing,π. Enriched targets, Ge(Li) detectors.     

Intermediate state perturbation in low temperature nuclear orientation

This paper deals with the perturbation of low temperature nuclear orientation in an intermediate state by an interaction not axially symmetric around the orientation axis. The directional distribution of the emitted radiation is factorized into initial orientation tensors and perturbation factors known from perturbed angular correlation theory. Low temperature nuclear orientation coefficients have been calculated numerically for¹¹¹Cd in a polycrystalline sample with axially symmetric electric field gradient. Nuclear orientation experiment on¹¹¹In in indium host confirms theoretical perturbation predictions and demonstrates the sensitivity of the method on different parameters. Moreover this orientation allows the determination, in magnitude and sign of¹¹¹In (ground state) nuclear magnetic moment: = +5.48(10)_n.     

High spin shell model excitations in149Gd

The high spin level structure of the three-neutron nucleus¹⁴⁹Gd has been investigated by in-beamγ-ray and electron spectroscopy with (α, xn) reactions. The observed levels are characterized as members of the shell model multipletsνf ₇ ^2/3 ,νh _9/2 f ₇ ^2/2 ,νf ₇ ^2/3 ×3^?,νh _9/2 f ₇ ^2/2 ×3^?, and tentativelyνf ₇ ^2/3 ×(3^?)². The energies of theν f ₇ ^2/3 states agree only moderately with those calculated using empirical two-nucleon interactions taken from¹⁴⁸Gd, which indicates the importance of long range contributions already atN=85.     

Atomic masses of rare earth isotopes145Pm,145Sm and151Gd,derived from decay measurements of145Sm and151Gd

The comparison of experimental with calculated K-capture probabilities yielded the decay energies of¹⁴⁵Sm and¹⁵¹Gd,Q _EC=622(5) and 463(3) keV, respectively. Earlier discrepancies in the mass adjustment of these isotopes were removed and adjusted masses for¹⁴⁵Sm,¹⁴⁵Pm and¹⁵¹Gd derived. In the decay of¹⁵¹Gd five newγ-rays were found and the half-life remeasured to be 129(4) d.     

Implantation temperature,dose and sample quality effects in nuclear orientation experiments

For samples prepared by ion implantation the dependence of the quality of the sample on parameters as implantation temperature, implantation dose and enthalpy of solution of the impurity-host system is discussed. Results from nuclear orientation experiments with the systems BiFe, CsFe and BrFe are presented and compared with recent channeling results and present information on the implantation process from computer simulations.     

Low temperature anomaly in Sc0.995Gd0.005H1.9

Gd³⁺ electron spin resonance linewidths and X-ray powder patterns have been determined from liquid nitrogen to room temperature on a hydrite of nominal composition Sc_0.995Gd_0.005H_1.9. These measurements reveal anomalous behavior below 140 K suggesting a phase transition.     

Magnetic dipole moments of the147, 149Gd ground states

Nuclear orientation measurements at low temperatures have been carried out on radioactive isotopes^{147, 149}Gd in Fe and Gd. The initial-state orientation coefficients determined from the measured gamma-ray anisotropies yield the magnetic dipole moments of the¹⁴⁷Gd and¹⁴⁹Gd ground states to be 1.02(9) and 0.88(4), _N, respectively. These values follow the systematics of the 7/2^– state magnetic moments of the odd-A nuclei in this region.     

Nuclear orientation of152,154Tb in gadolinium

The anisotropy in the directional distribution of gamma-rays from the decay of^152,154Tb oriented in a gadolinium matrix at low temperatures, has been measured at the angles of 0 and π/2 with respect to the applied magnetic field direction at temperature of (15±1) mK. Unambiguous values of spin have been deduced for several levels in¹⁵²Gd. Multipole mixing ratios of many gamma-ray transitions occurring in¹⁵²Gd have been found and results are compared with the similar transitions in^150,154,156Gd and they are discussed in terms of the rotational-vibrational model and dynamic deformation theory based on the Strutinsky method. Our results confirm the spin value of 0 for 21·4 h isomer in¹⁵⁴Tb and they establish the spin value of 3 for the 2277·0 and 2336·1 keV levels and the spin value of 4 for the 2416·3 keV level in¹⁵⁴Gd.