共查询到20条相似文献,搜索用时 62 毫秒
1.
I. C. Girit G. D. Alton C. R. Bingham H. K. Carter M. L. Simpson J. D. Cole W. L. Croft J. H. Hamilton E. F. Jones P. M. Gore J. Kormicki H. Xie B. D. Kern K. S. Krane Y. S. Xu P. F. Mantica Jr. B. E. Zimmerman W. G. Nettles E. F. Zganjar M. O. Kortelahti W. B. Newbolt 《Hyperfine Interactions》1988,43(1-4):151-156
The UNISOR on-line nuclear orientation facility (UNISOR/NOF) consists of a3He−4He dilution refrigerator on line to the isotope separator. Nuclei are implanted directly into a target foil which is soldered
to the bottom accessed cold finger of the refrigerator. A 1.5 T superconducting magnet polarizes the ferromagnetic target
foils and determines the axis of symmetry. Up to eight gamma detectors can be positioned around the refrigerator, each 9 cm
from the target. A unique feature of this system is that the k=4 term in the directional distribution function can be directly
and unambigously deduced so that a single solution for the mixing ratio can be found. The first on-line experiment at this
facility reported here was a study of the decay of the191Hg and193Hg isotopes. 相似文献
2.
Anna Nikiel Peter Blümler Werner Heil Manfred Hehn Sergej Karpuk Andreas Maul Ernst Otten Laura M. Schreiber Maxim Terekhov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2014,68(11):1-12
We describe a 3He magnetometer capable to measure high magnetic fields (B> 0.1 T) with a relative accuracy of better than 10-12. Our approach is based on the measurement of the free induction decay of gaseous, nuclear spin polarized 3He following a resonant radio frequency pulse excitation. The measurement sensitivity can be attributed to the long coherent spin precession time T2 ? being of order minutes which is achieved for spherical sample cells in the regime of “motional narrowing” where the disturbing influence of field inhomogeneities is strongly suppressed. The 3He gas is spin polarized in situ using a new, non-standard variant of the metastability exchange optical pumping. We show that miniaturization helps to increase T2 ? further and that the measurement sensitivity is not significantly affected by temporal field fluctuations of order 10-4. 相似文献
3.
Y. Totsuka H. Baba J. A. Behr T. Iguri M. Ikeda T. Kato H. Kawamura R. Kishi C. D. P. Levy Y. Nakaya K. Ninomiya H. Nishio J. Onishi R. Openshaw M. Pearson E. Seitaibashi S. Tanaka R. Tanuma T. Toyoda K. Watanabe J. Murata 《Physics of Particles and Nuclei》2014,45(1):244-248
The MTV experiment (Mott Polarimetry for T-Violation Experiment) is running from 2009 at TRIUMF, which aims to search a large non-standard T-Violation in polarized nuclear beta decay. Existence of transverse polarization of electrons emitted from polarized 8Li nuclei, which are produced at TRIUMF-ISAC and stopped inside an aluminum stopper, is investigated. We utilize a Mott polarimeter consists of a planer drift chamber, measuring backward scattering left-right asymmetry from a thin lead analyzer foil. In this paper, preliminary results from the first physics run performed in 2010 are described. 相似文献
4.
P. Herzog H.-R. Folle K. Freitag M. Reuschenbach H.U. Schmidt 《Physics letters. A》1977,62(4):245-246
197mHg was implanted in a iron foil at T<0.5 K. Subsequently a nuclear magnetic resonance experiment was performed in situ. A fraction of 32(4)% of the total number of implanted nuclei could be resonated. The small line width Γ=1.13(18) MHz indicates, that these nuclei experience no perceptible quadrupole interaction from their surroundings. 相似文献
5.
M. Lindroos J. Billowes C. Broude G. Goldring H. Haas M. Hass L. Mueller M.R. Pearson L. Weissman 《Hyperfine Interactions》2000,129(1-4):109-118
We report here on an ongoing experimental program initiated at the ISOLDE facility at CERN for the measurement of magnetic
moments of short-lived radionuclides, with the emphasis on magnetic moments of mirror nuclei in far-from-stability regions.
The nuclei are polarized by the tilted foil technique and the resulting 0–180○ βasymmetry is monitored as a function of rf frequency applied in an NMR setup. In order to achieve sufficiently high energy
for transmission through the foils, the experimental setup is mounted on a high voltage platform. The first experiment in
this program was the measurement of the βasymmetry and the NMR resonance for the ground state of 23Mg (I=3/2, T1/2=11.3 s), yielding μ=−0.533(6) nm. Improvements to the experimental setup are presently being designed, to be used in conjunction
with the new developments at ISOLDE for obtaining high charge-state ions from the EBIS (REX-ISOLDE) ion source. This will
help pave the way for measurements of magnetic moments of T=3/2 nuclei in the s–d shell and of T=1/2 f-shell nuclei. The study
of relaxation times and other solid-state phenomena in semiconductors and other materials of interest using this technique
is also contemplated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
J. Mertens H. Ackermann D. Dubbers P. Heitjans A. Winnacker P. von Blanckenhagen 《Zeitschrift für Physik A Hadrons and Nuclei》1973,262(3):189-210
Polarized110Ag nuclei are produced in the silver halides by capture of polarized neutrons at temperatures below 30 K and magnetic field strengths up to 6 kOe. The depolarization process is studied by observation of the β decay asymmetry as a function of magnetic field, temperature and of the radio frequency field strength in NMR signals. The depolarization is caused by a field dependent deorientation process and by temperature dependent spin-lattice relaxation. The deorientation is due to a succession of coupling steps of the nuclear spin with electromagnetic fields of defects generated as a consequence of the capture process, and the field dependence of the polarization can be understood as a decoupling curve. The temperature dependence of the spin-lattice relaxation is in accordance with the theory of quadrupolar relaxation above 18 K if an empirical phonon spectrum is used for the calculation. At lower temperatures the experimental relaxation rate is anomalously high, which may be due to resonance modes connected with recoil lattice defects. 相似文献
7.
In order to polarize radioactive nuclei implanted in a highly polarized protonic target, it is proposed to use methods for the dynamical orientation of nuclei. The angular distribution of photons that originate from the cascade beta-gamma decay of the 22Na(3+) state in a strong magnetic field is calculated. It is shown that, if the populations of Zeeman magnetic sublevels obey the Boltzmann distribution, the angular distribution of emitted photons is independent of the sign of spin temperature; at the same time, the tensor polarization of quadrupole nuclei occurring in the intrinsic field of a crystal causes a strong dependence of the anisotropy on the sign of spin temperature. A rich potential of a dynamical orientation for studying the magnetic structure of rare nuclei and the dynamics of their spin-spin interactions in dielectric host materials is demonstrated. Physical and technological advantages and disadvantages of the method in the on-line regime of the implantation of heavy nuclei are discussed. 相似文献
8.
Hutchison W.D. Harker S.J. Chaplin D.H. Funk T. Klein E. 《Hyperfine Interactions》1999,120(1-8):193-198
Combined host (∼95 at% enriched stable 57Fe) and very dilute impurity (∼0.01 at% radioactive 60Co) NMR signals have been obtained on the one sample of polycrystalline Fe foil utilising perturbations to the gamma anisotropy
from in situ thermally oriented 60Co nuclei for both resonances. The NMR-TDNO signals on the 57Fe sites have been followed down to applied magnetic fields well below the host magnetic saturation and exhibited two distinct
components; a strong, narrow homogeneous signal, superimposed over a broader inhomogeneous signal. The impurity 60Co57Fe inhomogeneous resonance has been studied with three pulse NMRON and the irreversible decay of the nuclear spin echo measured
as a function of applied magnetic field.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
I. Romanski I. Berkes D. E. Brown M. De Jesus R. Eder I. S. Grant E. Hagn P. Harding P. Herzog B. Hinfurtner B. Kastelein H. Postma J. Prinz P. Richards K. Schlösser N. J. Stone L. Vanneste E. Zech Nicole Isolde 《Hyperfine Interactions》1992,75(1-4):457-470
The methods of time-resolved and time-integral on-line nuclear orientation have been applied to study short lived nuclei with
the NICOLE facility (Nuclear Implantation into Cold On-Line Equipment) at ISOLDE-3 in CERN using beams of182–186Hg. The half-lives in these decay chains are of the order of seconds and therefore comparable to the spin-lattice relaxation
times of the nuclei in iron. As the relaxation rate depends strongly on the g-factor, g-factors of nuclei in the decay chains
can be deduced from the observation of the time evolution of γ-ray anisotropy. Using this technique the existence of an isomer
in184Au has been found and the g-factors of184Au,184mAu and182Au have been determined. Accurate half-lives have been extracted from the data.
Time-integral nuclear orientation has been observed for short lived as well as longer lived isotopes of the Hg decay chains.
From these measurements, after proper correction for incomplete relaxation, the magnetic moments of183mPt,183Ir and182Ir have been derived.
The applicability of the time-resolved nuclear orientation technique for nuclei far from stability and its possible limitations
is discussed. 相似文献
10.
Ions emerging from a stretched foil with their velocity vectorv at an oblique angle to the normaln (tilted foil geometry) are known to be polarized along the axisv×n. The electronic polarization of atomic configurations can influence the nucleus during flight in vacuum via the hyperfine
interaction. For a large number of polarizing foils and for very short interaction times, the resulting effects resemble a
pure precession in an external magnetic field and have been used to measureg-factors of short-lived nuclear high-spin levels. For long interaction times, a net nuclear polarization is induced and has
so far been utilized to determine signs of nuclear quadrupole moments of high-spin isomers and to investigate parity nonconservation
effects in93Tc. 相似文献
11.
T. Minamisono Y. Yasui T. Ohtsubo A. Kitagawa Y. Matsuo Y. Nojiri K. Matsuta S. Takeda 《Hyperfine Interactions》1990,59(1-4):153-156
The nuclear electric quadrupole moment of41Sc(Iπ=7/2−) was experimentally determined by use of the NMR detection in which the asymmetric β-ray distribution from spin polarized
nuclei was monitored. The magnetic interaction of the state with high external magnetic field and the nuclear quadrupole interaction
with the electric field gradient obtained in TiO2 crystal were studied. The field gradient seen to the implanted41Sc was measured independently by the high field NMR detection on the stable isotope45Sc located in the equivalent41Sc site with. |Q(41Sc;Iπ=7/2−)|=(0.120±0.006) b was determined. 相似文献
12.
P. M. Walker 《Hyperfine Interactions》1985,22(1-4):475-482
The Daresbury On-Line Isotope Separator (DOLIS) has recently been commissioned, in conjunction with the Nuclear Structure Facility (NSF) 20 MV tandem accelerator, and a3He-4He dilution refrigerator. First experiments are concentrating on a study of the decay of the neutron deficient iodine isotopes, extracted from a FEBIAD ion source and implanted at 60 keV into an iron host at 15 mK. As well as measuring iodine magnetic moments, the role of proton excitations across the Z=50 shell gap is being investigated in the even-even tellurium daughter nuclei. An on-line laser facility is also being developed, and first measurements have been made for unstable samarium isotopes 相似文献
13.
Electric quadrupole interactions on polarized 12B and 12N implanted in a Mg single crystal have been studied by a new method in which the nuclear depolarization due to level mixing caused by an external magnetic field is detected. 相似文献
14.
H.J. Jänsch 《Hyperfine Interactions》1997,106(1-4):219-228
Nuclear magnetic resonance has developed into a very powerful technique to study the structure and dynamics of atomic and
molecular systems, both in liquid and solid phase. However the investigation of single crystal surfaces with “conventional”
NMR methods is essentially impossible due to the small sample size of less than 1015 sites on a cm2. To overcome this for the important class of alkali adsorbates on metals and semiconductors, two methods are presented. Common
to both is the preparation of a highly nuclear spin polarized atomic beam of 6Li in the one case and 8Li in the other. The latter isotope is radioactive and undergoes a \beta‐decay with a halflife of 0.84 s. Li adsorbed on the
close packed Ru(001) surface is investigated. The T{in1} relaxation rate is the main observable and is used to deduce the
local electronic density of states (LDOS(EF,r=0)) and the Li diffusion barriers at low and high adsorbate coverage. The second experiment uses 6Li as an adsorbate, also studied on Ru(001). The nuclear polarization is measured by beam foil spectroscopy. A novel particle
detected (photon counting) Fourier‐Transform NMR technique is demonstrated, by observing the time dependent flux of circularly
polarized light emitted behind the foil after a 90\circ‐pulse has been employed at the surface. Development and prospects of the latter technique are presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
S. Karpuk F. Allmendinger M. Burghoff C. Gemmel M. Güldner W. Heil W. Kilian S. Knappe-Grüneberg Ch. Mrozik W. Müller E. W. Otten M. Repetto Z. Salhi U. Schmidt A. Schnabel F. Seifert Yu. Sobolev L. Trahms K. Tullney 《Physics of Particles and Nuclei》2013,44(6):904-908
Polarization of 3He gas by means of optical pumping is well known since the early 1960s with first applications in fundamental physics. Some thirty years later it was discovered, that one can use hyperpolarized 3He as contrast agent for magnetic resonance imaging of the lung. The wide interest in this new method made it necessary to find ways of polarizing 3He in large quantities with high polarization degrees. A high performance polarizing facility has been developed at the University of Mainz, designed for centralized production of hyperpolarized 3He gas. We present the Mainz concept as well as some examples of numerous applications of spin polarized 3He in fundamental research and medical applications. 相似文献
16.
G. M. Gurevich A. L. Erzinkyan V. P. Parfenova 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(4):520-525
Low-temperature spin orientation of radioactive nuclei is a nuclear spectroscopic method that allows us to obtain experimental
data on nuclei and extranuclear fields. We present the results from measuring the angular anisotropy of α radiation emitted
by transuranium nuclei of 253,254Es, 255Fm, 241,243Am, along with that of γ radiation from 250Bk nuclei oriented in an iron matrix at temperatures of 10–300 mK. The data allow us to establish the relation between the
mechanism of α decay and nuclear deformation and to compare them to the theoretical data. We also measure the energy of magnetic
hyperfine splitting for the investigated nuclei, and find the magnetic hyperfine field value for Es in Fe to be |B
hf
| = 396(32) T. The nuclear magnetic moment for 254Es was determined, and its value was |μ(254Es)| = 4.35(41)μ
N
. 相似文献
17.
C. Gemmel W. Heil S. Karpuk K. Lenz Ch. Ludwig Yu. Sobolev K. Tullney M. Burghoff W. Kilian S. Knappe-Grüneberg W. Müller A. Schnabel F. Seifert L. Trahms St. Bae?ler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,57(3):303-320
We discuss the design and performance of a very sensitive low-field magnetometer based on the detection of free spin precession of gaseous, nuclear polarized 3He or 129Xe samples with a SQUID as magnetic flux detector. The device will be employed to control fluctuating magnetic fields and gradients in a new experiment searching for a permanent electric dipole moment of the neutron. Furthermore, with the detection of the free precession of co-located 3He/129Xe nuclear spins it can be used as ultra-sensitive probe for non-magnetic spin interactions, since the magnetic dipole interaction (Zeeman-term) drops out. Characteristic spin precession times T2 * of up to 60 h were measured. The achieved signal-to-noise ratio of more than 5000:1 leads to an expected sensitivity level (Cramer-Rao lower bound) of δB≈1 fT after an integration time of 220 s and of δB≈10-4 fT after one day. By means of a co-located 3He/129Xe magnetometer, noise sources inherent in the magnetometer could be investigated, showing that CRLB is fulfilled, at least down to δB≈10-2 fT. The reason for such a high sensitivity is that free precessing 3He (129Xe) nuclear spins are almost completely decoupled from the environment. Therefore, this type of magnetometer is particularly attractive for precision field measurements where long-term stability is required. 相似文献
18.
R. I. Dzhioev B. P. Zakharchenya V. L. Korenev P. E. Pak M. N. Tkachuk D. A. Vinokurov I. S. Tarasov 《JETP Letters》1998,68(9):745-749
Dynamic polarization of 31P nuclei is observed in a self-organized system of InP islands grown by metalorganic-hydride epitaxy in an InGaP matrix. The
polarized nuclei produce an effective magnetic field which acts on the polarization of the excitonic radiation. Optical detection
of the magnetic resonance signal from 31P nuclei in the crystal lattice of nanosize InP islands is successfully carried out.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 9, 711–714 (10 November 1998) 相似文献
19.
The temperature dependence of the precession of the angular correlation of decay gamma rays from swift150Sm (2
1
+
) ions traversing a gadolinium foil has been found to be proportional to the foil magnetization, supporting the assertion
that the transient hyperfine magnetic field acting on these ions is proportional to the magnetization of the hosts (iron or
gadolinium). Similar experiments on194Pt (2
1
+
) ions traversing iron and gadolinium foils are consistent with both the magnetic moment obtained from Rutgers experiments
on iron and with a hyperfine field at Pt ions larger for gadolinium than for iron foils, in agreement with the Chalk River
parametrization for heavy nuclei traversing gadolinium foils. Finally, the magnetic moments of the 2
1
+
states in144–150Nd,145,150Sm and152Gd have been measured. These data support the evidence of shell closure atZ=64 forN≤88 andZ=50 forN>90. 相似文献
20.
L.M. Chirovsky W.P. Lee A.M. Sabbas J.L. Groves C.S. Wu 《Physics letters. [Part B]》1980,94(2):127-130
The 60Co nuclei in a thin permendur foil were polarized by a pair of orthogonal magnetic flux loops at ultralow temperatures. The observed angular distribution and the asymmetry factor (Aexp = ?1.01 ± 0.02) are in excellent agreement with theoretical predictions of (1 + α cos θ) dependence and Atheory = ?1.0. 相似文献