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 of149, 151Gd in gadolinium

^{149, 151}Gd fused in gadolinium metal have been oriented at low temperature. The main results are: ¦ (¹⁴⁹Gd,7/2^–¦=0.97(6)_N, ¦(¹⁵¹Gd,7/2^–¦= 0.77(6)_N and I(¹⁴⁹Eu,939 keV)=7/2. Some M1/E2 and E2/M3 mixing ratios in Eu daughter nuclei are also established.     

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 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 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 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.     

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.     

Electron capture ratios in206Bi

The level scheme of⁹⁷Tc has been investigated by observing theγ-rays following the decay of 2.9-d⁹⁷Ru.γ-singles andγγ-coincidence measurements were carried out with Ge(Li)-detectors. The time difference of coincident γ-rays was measured as a third parameter. From the coincidence events, the intensities ofγγ-cascades were extracted. The⁹⁷Ru decay gives rise to 18γ-lines which could be fitted into a level scheme of⁹⁷Tc consisting of 9 levels. Spin and parity assignments of the levels were made from log(ft) values andγ-ray branching ratios. Discrepancies concerning the energy of the first 3/2^? state and the existence of a 946 keV level are discussed.     

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.     

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.     

Nuclear orientation of156Tb in gadolinium matrix

The anisotropy of the angular distribution of gamma-rays from the decay of¹⁵⁶Tb, 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 in the range of temperatures from 14·6 to 68·4 mK. The temperature dependence of anisotropy was measured for the first time. The parameters of hyperfine magnetic dipole and electric quadrupole splittings have been determined and the values of the magnetic dipole moment ¦Μ¹⁵⁶¦=(9·6±1·3)×10^?27 J/T and the electric quadrupole momentQ ¹⁵⁶=(2·9±0·9)×10^?28 m² of the¹⁵⁶Tb ground state have been calculated. Multipole mixing ratios andB(E2) branching ratios of many gamma-ray transitions occurring in¹⁵⁶Gd have been found and the results have been discussed in terms of the rotational-vibration and pairing-plus-quadrupole models.     

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 magnetic structure of erbium iron garnet

The magnetic and crystallographic structure of erbium iron garnet {Er₃}[Fe₂](Fe₃)O₁₂ has been refined simultaneously from powder and single crystal neutron diffraction data. At 5 K the ferrimagnetic structure has a spin direction parallel to [100]. Magnetic moments of iron and erbium and canting angles for the erbium sublattices were derived in space groupI4₁/acd for 5 K<T<65 K. The magnetic moments of the two erbium sites are 6.9 _B and 4.3 _B at 5 K. An indication of further symmetry reduction of the magnetic structure from tetragonal to orthorhombic below 5 K is discussed.     

Alpha decay of 210At to levels in 206Bi

The α-decay of ²¹⁰At has been investigated with α-γ coincidence techniques. Spins of ²⁰⁶Bi levels below 500 keV have been deduced from recent electron-capture studies of ²⁰⁶Po, reaction studies of ²⁰⁶Bi and present results. Calculations of the α-decay rates and electromagnetic transition probabilities using wave functions in a. truncated configuration space are compared with the experimental results.     

The orientation of porphins in n-alkane Shpolskii hosts

When a solution of a porphin in n-octane is slowly frozen the guests predominantly occupy a single site (A) in which the porphin has been shown to replace a number of host molecules displaced along the b-direction; if the solution is quickly frozen the optical spectra reveal the presence of a second site (B). In the present paper it is shown that the occurrence of these two types of sites, A and B, is a common phenomenon throughout the series from n-heptane (C₇) to n-decane (C ₁₀) as hosts and phenomenological criteria are formulated to distinguish between the two kinds of sites.

The orientation of palladiumporphin (PdP) in the A and B sites of a C₇ host is determined from Zeeman experiments on the S ₁← S ₀ and T ₀ →S ₀ transitions in a single crystal of C₇ doped with PdP. The porphin nuclei in the B sites replace a number of alkanes displaced along the a-axis. In the course of the experiments signals related to a third type of site, B', grew in intensity in the spectra. This site is coplanar with the B site and it differs from the latter by an in-plane rotation of the trapped molecule over 20°. The origins of the S ₁ ←S ₀ transition for the two types of site are assigned for H₂P, ZnP and PdP as solutes in C₇, C₈, C₉ and C₁₀ as hosts.

Finally, the Zeeman shifts observed in the S ₁ ←S ₀ transition of PdP in the three sites of C₇ yield an effective orbital angular momentum for PdP in the state S ₁ of (4·4 ± 0·1)?, in excellent agreement with previous determinations.     

NMR/ON of206Bi implanted at T < 0.2 K and at room temperature into nickel

NMR/ON has been observed for²⁰⁶BiNi with samples prepared by implantation at T<0.2 K and at room temperature. The integrated destruction of anisotropy for the sample implanted at 290 K is only about half of that for the on-line implanted sample but the resonance line is less broad and has a narrow component with centre frequency _L= 223.62(10) MHz for zero external field. With the known g-factor of²⁰⁶Bi we derive from this frequency the hyperfine field of BiNi as B_hf=38.3(4) T.     

Dynamic nuclear polarization and nuclear orientation in an antiferromagnet

Dynamic nuclear polarization is a well established technique which has been used to produce polarized targets for experiments in nuclear physics. This paper suggests experiments of a similar type but involving the nuclear magnetic resonance of two isotopes, one stable and the other radioactive. The substance is an antiferromagnet, dysprosium phosphate, at temperatures below the Néel point, where line widths are comparatively small. The effect may be detected through changes in the rate of gamma ray emission observed by a nuclear orientation experiment.