Fe-57 Mossbauer spectroscopic and magnetic studies of R3Fe29-xVx (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy)

Mossbauer spectra for Fe atoms in the series of R3Fe29-xVx (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy) compounds were collected at 4.2 K. The ratio of 14.5 T/mu(B) between the average hyperfine field B-hf and the average Fe magnetic moment mu(Fe)(MS), obtained from our data, in Y3Fe29-xVx is in agreement with that deduced from the RxTy alloys by Gubbens et al. The average Fe magnetic moments mu(Fe)(MS) in these compounds at 4.2 K, deduced from our Mossbauer spectroscopic studies, are in accord with the results of magnetization measurement. The average hyperfine field of the Fe sites for R3Fe29-xVx at 4.2 K increases with increasing values of the rare earth effective spin (g(J) - 1) J, which indicates that there exists a transferred spin polarization induced by the neighboring rare earth atom.

Mossbauer spectroscopy study of Fe-57 in R3Fe29-xTx (R=Y, Ce, Nd, Sm, Gd, Tb and Dy; T=V and Cr)

Fe-57 Mossbauer spectra for the Fe atoms in the R3Fe29-xTx (R=Y, Ce, Nd, Sm, Gd, Tb, Dy; T=V, Cr) compounds were collected at 4.2 K. The analysis of Mossbauer spectra was based on the results of magnetization and neutron powder diffraction measurements. The average Fe magnetic moments at 4.2 K, deduced from our data, are in accord with magnetization measurements. The average hyperfine field of Tb3Fe29-xCrx (x=1.0, 1.5, 2.0, and 3.0) decreases with increasing Cr concentration, which is also in accordance with the variation of the average Fe magnetic moment in the Tb3Fe29-xCrx compounds.

Crystallographic and magnetic properties of hydride R3Fe29-xTxHy (R=Y, Ce, Nd, Sm, Gd, Tb and Dy; T=V and Cr)

The crystallographic and intrinsic magnetic properties of hydride R3Fe29-xTxHy (R=Y, Ce, Nd, Sm, Gd, Tb, and Dy; T=V and Cr) have been investigated. The lattice constants and the unit cell volume of R3Fe29-xTxHy decrease with increasing R atomic number from Nd to Dy, except for Ce, reflecting the lanthanide contraction. Regular anisotropic expansions, mainly along the a- and b-axis rather than along the c-axis, are observed for all the compounds upon hydrogenation. Hydrogenation leads to an increase in Curie temperature. First-order magnetization processes (FOMP) occur in magnetic fields of around 1.5 T and 4.0 T at 4.2 K for Nd3Fe24.5Cr4.5H5.0 and Tb(3)Fc(27.0)Cr(2.0)H(2.8), and around 1.4 T at room temperature for Gd3Fe28.0Cr1.0H4.2 Abnormal crystallographic and magnetic properties of Ce3Fe29-xTxHy suggest that the Ce ion is non-triply ionized.

重离子辐照对人舌鳞癌Tb细胞周期的影响

目的探讨重离子辐照对人舌鳞癌Tb细胞周期进程的影响及受照剂量和修复时间的关系。方法采用流式细胞仪检测不同剂量重离子辐照后人舌鳞癌Tb细胞不同时间点的细胞周期变化。结果人舌鳞癌Tb细胞经重离子辐照后,出现G2/M期明显阻滞,阻滞程度具有剂量和时间依赖性,G2/M期阻滞在24h时与照射剂量呈正相关(r=0.935,P<0.05)。当受到0.5、1Gy照射后,细胞在12h到达阻滞高峰,24h时最大峰值回落。辐照剂量分别为2、4Gy时,细胞表现为G2/M的明显阻滞,未出现阻滞解除现象。结论人舌鳞癌Tb细胞经重离子照射后存活后代生长延缓,放射敏感性增高,呈G2/M期阻滞。

~(140)Tb和~(141)Dy的β缓发质子衰变以及~(143)Dy的自旋宇称

利用40Ca+106Cd融合蒸发反应产生了近质子滴线核140Tb和141Dy,配合氦喷嘴带传输系统采用“质子-γ”符合方法观测了它们的β缓发质子衰变,其中包括半衰期、质子能谱和衰变到第二代子核不同低位态的分支比．通过统计理论拟合提取了140Tb和141Dy的基态自旋宇称分别为7±和9／2±．另一方面,用Woods-Saxon Strutinsky方法计算了这两种核限制组态的势能面,由此得到140Tb和141Dy的基态自旋宇称分别为7+和9／2-．此外用同一方法还计算了143Dy的核势能面,从中看出143Dy存在有自旋宇称为1／2+的基态和一个激发能为198keV的11／2-的同质异能态．该结果与2003年Eur．Phys．J． A16:347-351中的143Dy衰变实验数据相符．

原子核~(145)Tb的多准粒子激发态

利用能量为165 MeV的32S束流, 通过反应118Sn(32S, 1p4n)布居了145Tb的高自旋态. 基于标准在束核谱学实验测量结果, 首次建立了激发能高达 7.4 MeV的145Tb能级纲图. 145Tb的能级结构具有球形原子核的特征, 其高自旋态是由单粒子激发形成的. 根据邻近N = 80同中子素核结构的系统性, 采用一个11/2h价质子与偶偶核芯144Gd的弱耦合很好地解释了145Tb激发能在2 MeV以下的能级结构. 利用多准粒子壳模型组态解释了激发能在2 MeV以上的晕态和部分近晕态能级.

~(146)Tb的能级结构研究

利用能量为161—175MeV的~(32)S束流,通过反应~(118)Sn(~(32)S,1p3n)~(146)Tb研究了双奇核~(146)Tb的高自旋态能级结构。实验进行了γ射线的激发函数、γ射线的各向异性度、X-γ和γ-γ-t符合测量。基于这些测量结果,建立了激发能达8390kev的~(146)Tb核的能级纲图,其中包括新发现的41条γ射线和新建立的27个能级,并指定了~(146)Tb新发现能级的自旋值。用一个h_(11/2)价质子和一个h_(11/2)~(-1)价中子空穴耦合、πh_(11/2)υh_(11/2)~(-1)与~(146)Gd核实激发态的耦合对~(146)Tb的能级结构进行了定性地讨论。