Gamow-Teller beta decay of 105Sn

The β-decay of ¹⁰⁵Sn was re-investigated at the ISOL facility of GSI Darmstadt by using a total absorption spectrometer. The experimental results include the half-life and β-delayed proton branching ratio of 32.7(5)s and 1.1(4) ^. 10^-4, respectively, and the contribution of electron capture to the ¹⁰⁵Sn decay of 0.420(35). The Gamow-Teller strength distribution peaking at 3.6MeV was measured, yielding a summed Gamow-Teller strength of 3.0(4). The latter data are discussed in comparison with shell-model predictions based on an empirical interaction.     

Beta decay of 94Pd and of the 71 s isomer of 94Rh

The β decay of ⁹⁴Pd and of the 71s isomer of ⁹⁴Rh was investigated by using total γ-ray absorption techniques. Several levels in ⁹⁴Rh are established, including a new low-lying isomer characterized by a half-life of 0.48(3)μs and a de-exciting transition of 55keV. E2 multipolarity is determined for this transition by measuring the intensities of its γ-rays and the characteristic X-rays from its electron conversion. On the basis of the measured reduced β-decay transition rates to known ⁹⁴Ru levels and shell model considerations, the spin-parity of the 71s and the 0.48μs isomers of ⁹⁴Rh is assigned to be (4⁺) and (2⁺), respectively. The β-decay strength distributions measured for ⁹⁴Pd and the 71s isomer of ⁹⁴Rh yield Q _EC values of 6700(320) and 9750(320)keV for these decays and give evidence for the population of those states below and above the magic N = 50 gap that belong to both components of the 0g spin-orbit doublet.     

Letter: Antisymmetric Tensor Contribution to the Muon g − 2

We investigate the Kalb-Ramond antisymmetric tensor field as a solution to the muon g – 2 problem. In particular we calculate the lowest-order Kalb-Ramond contribution to the muon anomalous magnetic moment and find that we can fit the new experimental value for the anomaly by adjusting the coupling without affecting the electron anomalous magnetic moment results.     

Molecular motion in some radiolabelled dipeptides: a muon spin relaxation study

Activation parameters were determined for the dynamics of radicals formed by muonium addition to glycylglycine (GlyGly; H₃N⁺CH₂CONHCH₂CO₂^?) and the doubly protected alanylalanine derivative [Boc‐AlaAla‐Bz; Bu^tOCONHCH(Me)CONHCH(Me)CO—O—CH₂Ph]. GlyGly forms an adduct by muonium addition to the amide carbonyl group which isomerizes by flipping the muon between opposite sides of the molecule, requiring an activation energy of 20.4 kJ mol^?1. In Boc‐AlaAla‐Bz, muonium addition to the benzene ring of the benzyl (—CH₂Ph) group occurs, exhibiting an activation energy of 9.4 kJ mol^?1, believed to be from torsion about the C—Ph bond. Copyright © 2002 John Wiley & Sons, Ltd.     

β-decay half-lives of very neutron-rich isotopes of elements from Ti to Ni

The unknown β-decay half-lives of 22 isotopes far off stability (5 < T _Z < 10) in the region from Ti to Ni were measured at GSI, Darmstadt. The nuclei were produced in a fragmentation reaction of 500 A.MeV ⁸⁶Kr-projectile impinging on a thick Be target. The isotopes of interest were separated and identified with the fragment separator, FRS, by a combination of Bρ,Z, and ToF techniques. An additional range separation was performed by a selective implantation into granular detectors. The spatial and time correlations of the implant with the consecutively detected β-particles were used to determine the unknown half-lives. For nuclei far off stability, β-decay chains were measured and analyzed as well, leading to an even more reliable evaluation of the lifetimes. The large discrepancies found between the measured and the theoretical values emphasize that most recent theoretical work is not an improvement over calculations made almost a decade ago. Received: 1 October 1997     

High temperature magnetic order in zinc sulfide doped with copper

We report the first observation of magnetic order above room temperature in zinc sulfide doped with Cu²⁺ made by a simple sintering process and detected by ferromagnetic resonance (FMR), SQUID magnetometry and the μSR experiments. FMR study shows nonzero absorption above room temperature indicating a high value of Curie temperature. Field-cooled and zero-field-cooled magnetization data indicate a bifurcation at about 300 K. This temperature is considered to be the blocking temperature at ferromagnetic nanosized regions, which appear to exist in the sample of ZnS doped with copper. The muon spin rotation measurements confirm highly nonuniform magnetic order. It was shown that about 25% of the sample volume fraction exhibits strong magnetism.     

缪子多模态成像图像质量分析

缪子多模态成像有效利用了宇宙线缪子与材料相互作用产生的散射信息以及产生次级诱发中子的缪子信息.为对缪子多模态成像图像质量进行分析,基于GEANT4程序设置了探测模型,从缪子多重库仑散射模块和缪子诱发中子模块两部分对探测模型可靠性进行了验证,开发了缪子多模态成像模拟程序,得到了重建图像.成像12 h可达到4 mm的空间分辨率,成像时间在小时量级可清晰分辨边长10 cm的²³⁵U立方体和其他常见的高、中、低原子序数材料立方体.经过12 h成像时间,包覆模型的缪子散射成像图像会造成误判,但缪子多模态成像图像能够正确反映²³⁵U材料存在.不同成像时间内,缪子多模态成像图像的结构相似性指标均优于单一成像方法成像图像.研究结果表明与缪子散射成像图像和诱发中子符合的缪子成像图像相比,缪子多模态成像图像有更好的成像质量,能够适应更复杂的成像场景,在特殊核材料的检测识别方面更有优势.     

Background study and Monte Carlo simulations for large-mass bolometers

Large-mass bolometers are today extensively used for dark matter and double beta decay searches, in both cases the ultimate experimental sensitivity is defined by the background level reached in such devices. The most common background sources and the techniques used for their identification and reduction are here reviewed, with a particular focus on double beta decay searches. The relevant role played by Monte Carlo simulations in this field is discussed. As a real case, the background optimization in the MiDBD experiment is described.     

Recent progress on isospin breaking corrections and their impact on the muon g-2 value

We describe some recent results on isospin breaking corrections which are of relevance for predictions of the leading order hadronic contribution to the muon anomalous magnetic moment ahμa d,LOwhen using τ lepton data.When these corrections are applied to the new combined data on the π±π0 spectral function,the prediction for aμha d,LObased on τ lepton data gets closer to the one obtained using e+e-data.     

A new basic motif in cyanometallate coordination polymers: structure and magnetic behavior of M(mu-OH2)2[Au(CN)2]2 (M=Cu, Ni)

The structures of two cyanoaurate-based coordination polymers, M(mu-OH(2))(2)[Au(CN)(2)](2) (M=Cu, Ni), were determined by using a combination of powder and single-crystal X-ray diffraction techniques. The basic structural motif for both polymers contains rarely observed M(mu-OH(2))(2)M double aqua-bridges, which generate an infinite chain; two trans [Au(CN)(2)](-) units also dangle from each metal center. The chains form ribbons that interact three dimensionally through CNH hydrogen bonding. The magnetic properties of both compounds and of the dehydrated analogue Cu[Au(CN)(2)](2) were investigated by direct current (dc) and alternating current (ac) magnetometry; muon spin-relaxation data was also obtained to probe their magnetic properties in zero-field. In M(mu-OH(2))(2)[Au(CN)(2)](2), ferromagnetic chains of M(mu-OH(2))(2)M are present below 20 K. Interchain magnetic interactions mediated through hydrogen bonding, involving water and cyanoaurate units, yield a long-range magnetically ordered system in Cu(mu-OH(2))(2)[Au(CN)(2)](2) below 0.20 K, as indicated by precession in the muon spin polarization decay. Ni(mu-OH(2))(2)[Au(CN)(2)](2) undergoes a transition to a spin-glass state in zero-field at 3.6 K, as indicated by a combination of muon spin-relaxation and ac-susceptibility data. This transition is probably due to competing interactions that lead to spin frustration. A phase transition to a paramagnetic state is possible for Ni(mu-OH(2))(2)[Au(CN)(2)](2) upon application of an external field; the critical field was determined to be 700 Oe at 1.8 K. The dehydrated compound Cu[Au(CN)(2)](2) shows weak antiferromagnetic interactions at low temperatures.