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1.
报道了用“联合D0 和D+单双标记”测定衰变分支比的方法 .基于北京谱仪 (BES)在北京正负电子对撞机 (BEPC)质心系能量s =4 .0 3GeV处获取的数据 ,利用联合D0 和D+单双标记的方法 ,可以测定D0 和D+介子单举和遍举衰变分支比 .作为该方法的应用举例 ,利用BES实验组发表的数据 ,在 90 %置信度的情况下 ,测得D+→e+ν衰变过程分支比的上限为Br(D+→e+ν) <1 .6% .此上限值与BES曾发表的结果一致 .  相似文献
2.
通过熔合蒸发反应128Te(19F,4nγ)布居了143Pm的高自旋态,利用在束γ谱学方法,对143Pm的高自旋态核结构进行了研究.测量了γ射线单谱和γ-γ符合谱,并进行了γ射线各向异性以及DCO比率分析,建立了激发能高达10535.4keV的能级纲图,其中包括新发现的32条γ射线和17个新能级.用弱耦合模型对143Pm的晕态能级结构进行了解释.  相似文献
3.
利用能量为60-80MeV的12C束流,通过197Au(12C,3n) 206 At反应研究了206At核的高自旋能级结构. 用7台BGO(AC)HPGe探测器和一台用于探测低能γ射线的平面型HPGe探测器进行了γ射线的激发函数、γ-γ-t符合及γ射线的角分布测量. 基于这些测量,首次建立了包括25条γ跃迁的206At高自旋能级纲图. 确定了一个半寿命为(908±400)ns、自旋和宇称为10-的同质异能态. 基于较重的双奇核 208,210At能级结构的系统性,对206At的10-同质异能态进行了讨论.  相似文献
4.
胡先权  许 杰  罗 光  马 燕 《中国物理》2007,16(12):3631-3636
The model of the Coulomb dressed potential is applied to solving the problem of electron scattering for simplifying the calculation in the electrostatic field and the excimer laser field. The introduction and the application of the model are based on the electric dipole approximation, so the contribution of the electric multipole is neglected. In this paper, rigorous analysis and deduction are carried out for the introduction of the dressed Coulomb potential into the laser field. It is found that the introduction of the dressed potential in the fractional form is feasible only when the laser field (not including far ultraviolet field and x-ray) is a weak field, i.e. the quiver radius of the free electron is smaller than the atomic scale. In addition, the necessary analysis is also conducted of the limitation of the application of the Coulomb dressed potential.  相似文献
5.
报道了用“联合D0和D+单双标记”测定衰变分支比的方法.基于北京谱仪(BES)在北京正负电子对撞机(BEPC)质心系能量s=4.03GeV处获取的数据,利用联合D0和D+单双标记的方法,可以测定D0和D+介子单举和遍举衰变分支比.作为该方法的应用举例,利用BES实验组发表的数据,在90%置信度的情况下,测得D+→e+ν衰变过程分支比的上限为Br(D+→e+ν)<1.6%.此上限值与BES曾发表的结果一致.  相似文献
6.
利用能量为75—95MeV19F束流,通过反应128Te(19F,5nγ)142Pm研究了双奇核142Pm的高自旋态能级结构.实验中进行了γ射线的激发函数、γ射线单谱和γγ符合测量.建立了激发能达7030.0keV的142Pm的能级纲图,其中包括新发现的25条γ射线和13个新能级.基于实验测量的γ跃迁各向异性度,建议了142Pm能级的自旋值.  相似文献
7.
简要介绍时间微分扰动角分布、瞬态场-离子注入扰动角分布、β-放射性探测的核磁共振和核电共振等原子核核矩测量方法及其在核结构研究中的应用, 给出了43Sc(19/2,3.1232MeV,0.45μs)同质异能态、84、86Zr和83Y高自旋态、17F(I=5/2+,T1/2=64.49s)、12B和12N镜核对的核矩测量和核结构研究例子.  相似文献
8.
利用能量为60-80MeV的~(12)C束流,通过~197An(~(12)C,3n)~206At反应研究了~206At核的高自旋能级结构.用7台BGO(AC)HPGe探测器和一台用于探测低能γ射线的平面型HPGe探测器进行了γ射线的激发函数、γ-γ-t符合及γ射线的角分布测量.基于这些测量,首次建立了包括25条γ跃迁的~206At高自旋能级纲图.确定了一个半寿命为(908±400)ns、自旋和宇称为10的同质异能态.基于较重的双奇核~(208,210 )At能级结构的系统性,对~(206)At的10~-同质异能态进行了讨论.  相似文献
9.
The recent discovery of high-temperature superconductivity in iron-based pnictides (chalcogenides) not only triggers tremendous enthusiasm in searching for new superconducting materials, but also opens a new avenue to the study of the Kondo physics. CeFeAsO is a parent compound of the 1111-type iron-based superconductors. It shows 3d-antiferromagnetic (AFM) ordering below ~ 139 K and 4f-AFM ordering below ~ 4 K. On the other hand, the phosphide CeFePO is a ferromagnetically correlated heavy-fermion (HF) metal with Kondo scale T K ~ 10 K. These properties set up a new platform for research of the interplay among magnetism, Kondo effect, and superconductivity (SC). In this review, we present the recent progress in the study of chemical pressure effect in CeFeAsO 1-y F y (y = 0 and 0.05). This P/As-doping in CeFeAsO serves as an effective controlling parameter which leads to two magnetic critical points, x c1 0.4 and x c2 0.92, associated with suppression of 3d and 4f magnetism, respectively. We also observe a turning point of AFM-FM ordering of Ce 3+ moment at x c3 0.37. The SC is absent in the phase diagram, which is attributed to the destruction to Cooper pair by Ce-FM fluctuations in the vicinity of x c1 . We continue to investigate CeFeAs 1-x P x O 0.95 F 0.05 . With the separation of x c1 and x c3 , this chemical pressure results in a broad SC region 0≤ x ≤ 0.53, while the original HF behavior is driven away by 5% F doping. Different roles of P and F dopings are addressed, and the interplay between SC and Ce-4f magnetism is also discussed.  相似文献
10.
The recent discovery of high-temperature superconductivity in iron-based pnictides (chalcogenides) not only trig- gers tremendous enthusiasm in searching for new superconducting materials, but also opens a new avenue to the study of the Kondo physics. CeFeAsO is a parent compound of the 1111-type iron-based superconductors. It shows 3d- antiferromagnetic (AFM) ordering below 139 K and 4f-AFM ordering below 4 K. On the other hand, the phosphide CeFePO is a ferromagnetically corelated heavy-fermion (HF) metal with Kondo scale TK 10 K. These properties set up a new platform for research of the interplay among magnetism, Kondo effect, and superconductivity (SC). In this review, we present the recent progress in the study of chemical pressure effect in CeFeAsOl_yFy (y = 0 and 0.05). This P/As-doping in CeFeAsO serves as an effective controlling parameter which leads to two magnetic critical points, Xcl -- 0.4 and Xc2 - 0.92, associated with suppression of 3d and 4f magnetism, respectively. We also observe a turning point of AFM-FM ordering of Ce3+ moment at Xc3 - 0.37. The SC is absent in the phase diagram, which is attributed to the destruction to Cooper pair by Ce-FM fluctuations in the vicinity of Xcl. We continue to investigate CeFeAsl-xPxO0.95Fo.os. With the separation of xcl and xc3, this chemical pressure results in a broad SC region 0〈 x 〈 0.53, while the original HF behavior is driven away by 5% F- doping. Different roles of P and F dopings are addressed, and the interplay between SC and Ce-4f magnetism is also discussed.  相似文献
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