缺中子稀土区滴线附近新的β缓发质子衰变

用重离子束³⁶Ar和³²S轰击缺中子同位素靶⁹²Mo,⁹⁶Ru和¹⁰⁶Cd产生了质子滴线附近的β缓发质子先驱核¹²⁵Nd,¹²¹Ce,¹²⁸Pm,¹²⁹Sm,¹³⁵Gd,¹³⁷Gd和¹³⁹Dy.配合氦喷嘴带传输系统用"p-γ"符合方法对它们进行了首次肯定的鉴别.它们的半衰期分别为:0.60(15)s,1.1(1)s,1.0(3)s,0.55(10)s,1.1(2)s,2.2(2)s和0.6(2)s.用统计模型理论计算对实验测定的¹²⁵Nd,¹²¹Ce,¹²⁹Sm,¹³⁵Gd,¹³⁷Gd和¹³⁹Dy的β缓发质子衰变的能谱和分支比进行了拟合.提取出¹²⁵Nd,¹²¹Ce,¹²⁹Sm,¹³⁵Gd,¹³⁷Gd和¹³⁹Dy的基态自旋-宇称分别为5/2^±,5/2^±,1/2⁺(或3/2⁺),5/2⁺,7/2^±和7/2⁺.实验初步指认的基态自旋(宇称值与Nilsson能级图的预言值相符间接表明这6个核素的基态具有大形变,形变参数β₂在0.3左右.     

140Tb和141Dy的β缓发质子衰变以及143Dy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.     

质子滴线附近的新核素129Pm

通过重离子引起的融合蒸发反应⁹²Mo(⁴⁰Ca,p2n)合成了稀土区未知核素¹²⁹Pm,并且配合氦喷嘴快速带传输系统利用X-γ符合方法对它进行了首次鉴别.实验观测到了经¹²⁹Pm的(EC+β⁺)衰变产生的对应于子核¹²⁹Nd中5/2^－→1/2^－跃迁的一条99keV γ线.根据这条99keV γ线的时间衰变曲线,提取出¹²⁹Pm的半衰期为(2.4±0.6)s.     

进一步指认近质子滴线核129Pm的衰变

2004年曾报道过利用⁴⁰Ca＋⁹²Mo融合蒸发反应产生了近质子滴线新核素Pm,并首次观测到它(EC+b+)衰变产生的能量为99keV的γ射线. 为了进一步确认上述指认，以下提供了三方面的新证据：1)在164－190MeV能量范围内测量了99keV衰变γ射线的激发函数;2)进行了交叉反应 ³⁶Ar＋⁹⁶Ru的实验,观察到了相同的99keV衰变γ射线；3)用Woods-Saxon Strutinsky方法计算了¹²⁹Pm的核势能面，其基态自旋宇称被预言为5/2^－，所以¹²⁹Pm的(EC＋b＋)衰变有利于馈送到子核¹²⁹Nd的5/2_－的低位态，这也与前期报道相符.     

160Gd(n,2n)159Gd和158Gd(n,p)158Eu反应截面测量

报道了在13.5—14.6MeV中子能区用活化法测得的¹⁶⁰Gd(n,2n)¹⁵⁹Gd和¹⁵⁸Gd(n,p)¹⁵⁸Eu的 反应截面值. 中子注量用⁹³Nb(n, 2n)⁹²m Nb反应截面得到. 由(13.5±0.2)MeV,(14.1±0.1)MeV和(14.6±0.2)MeV中子引起的¹⁶⁰Gd(n, 2n) ¹⁵⁹Gd反应截面值分别为(1940±83)mb, (2324±92)mb和(1983±77)mb, ¹⁵⁸Gd(n, p) ¹⁵⁸Eu反应截面值分别为(1.9±0.1)mb, (2.1±0.1)mb和(3.5±0.1)mb. 单能中子由T(d, n)⁴He反应获得.文中还列举了已收集到的数据以作比较.     

130Nd和140Tb的EC/β+衰变研究

利用能量为170MeV左右的³⁶Ar重离子束轰击⁹⁶Ru和¹⁰⁶Cd浓缩同位素靶,分别生成缺中子同位素¹³⁰Nd和¹⁴⁰Tb.借助氦喷嘴带传输系统,用X–γ和γ–γ符合方法,分离鉴别了这两种核素,并进一步测定了它们的衰变性质.得到¹³⁰Nd的半衰期为(13±3)s,首次建议了它的EC/β+衰变纲图,推测了其子核¹³⁰Pr的基态和低位能级的自旋宇称.修订了¹⁴⁰Tb的原有极简单的EC/β⁺衰变纲图并指认¹⁴⁰Tb的基态自旋宇称为7⁺.     

合成和研究滴线区新核素β延发质子先驱核121Ce

利用³²S束轰击⁹²Mo靶,熔合蒸发3n反应合成了¹²¹Ce.藉助于具有γ(X)-p-t符合测量的氦喷嘴反冲快速带传输系统进行分离和鉴别.实验定出¹²¹)Ce的半衰期为(1.1±0.1)s,观测到了¹²¹Ce的延发质子谱并近似估计了延发质子分支比为(1.0±0.5)%.     

14MeV钕的同位素反应截面的测量

报道了在13.5—14.6MeV中子能区用活化法以⁹³Nb(n,2n)^92mNb反应截面为中子注量标准测得的¹⁵⁰Nd(n,2n)¹⁴⁹Nd,¹⁴⁸Nd(n,2n)¹⁴⁷Nd和¹⁴²Nd(n,2n)¹⁴¹Nd的反应截面值.由13.5±0.2,14.1±0.1和14.6±0.2MeV中子引起的¹⁵⁰Nd(n,2n)¹⁴⁹Nd反应截面值分别为2037±85,1737±68,1657±65mb,¹⁴⁸Nd(n,2n)¹⁴⁷Nd反应截面值分别为1394±58,1416±54,1956±76mb,^{142Nd(n,2n)141Nd反应截面值分别为1501±59,1623±62,1764±111mb.单能中子由T(d,n)4He反应获得.文中还收集了已发表的数据以作比较.}     

93Pd的β缓发质子衰变

通过⁵⁸Ni(⁴⁰Ca,3n2p)反应合成等待点核⁹³Pd,采用氦喷嘴带传输系统加p-γ符合,观测到了它的β缓发质子衰变,测得其半衰期为(1.3±0.2)s.采用统计模型计算拟合了实验测得的β缓发质子能谱和布居到质子发射体子核不同终态的分支比,指认了⁹³Pd的基态自旋为9/2.用Woods-Xason Strutinsky方法计算了⁹³Pd的核位能面,其结果表明93?Pd基态自旋宇称可能为9/2⁺.     

对质子滴线核19Na的β延迟质子衰变的首次观察

由²⁰Ne(P,2n)¹⁹Na反应,对质子滴线核¹⁹Na进行了研究,实验在中国科学院高能物理研究所质子直线加速器上进行,首次观察到了¹⁹Na的β延迟质子衰变,测定其质子能量为1.10±0.08MeV,半衰期为47±20ms,它相应于¹⁹Na基态到¹⁹Ne的7.62MeV、T=3/2同位旋相似态的超允许β跃迁和由此态到¹⁸F基态的级联质子衰变.     

关于"太阳在银河系中所受引力与到银心距离r的关系"的讨论

讨论了银道面内的引力场强分布和太阳在银河系中所受引力与到银心距离r的关系，指出引力场强g并不是与r的平方成反比，这是由于银河系的大小和形状不能忽略造成的．强调了万有引力定律的适用条件．     

On the predictability of the positions of the convergence zones in the ocean

The disagreement between the experimental and calculated positions of the first convergence zone are known from many publications. The most probable cause for such a disagreement, namely, the incorrect specification of the input data for the calculations, is considered. The lack of simultaneity between the hydrological surveys of the region and the acoustic experiments is emphasized. The experimental data obtained by the author in five ocean regions are presented. These data characterize the diurnal variability of the distance from the source to the nearest boundary of the convergence zone. The relations proposed by different researchers for calculating the sound speed from the temperature, salinity, and hydrostatic pressure are analyzed. It is shown that these relations lead to a substantial difference in the estimated depth dependence of the hydrostatic gradient of the sound speed. The position of the first convergence zone is calculated for the propagation conditions determined by vertical temperature and salinity profiles with the subsequent recalculation of these profiles into sound speed profiles by using eight different formulas known from the literature. It is shown that different formulas lead to different values of the distance to the first zone; this difference is substantially greater than that between the calculations and experiment. The necessity of improving the recalculation relations in view of the experimental data on sound propagation in natural oceanic waveguides, including the data on the actual positions of the convergence zones, is emphasized.     

On the calculation of the bremsstrahlung in the region of the plasma frequency

On the basis of the classical theory of radiation produced in incomplete Coulomb interaction, a formula is derived for the coefficient of the bremsstrahlung of fully ionized plasma. In the region of rectilinear approximation a comparison is made with the results of the quantum formula derived from the Born approximation. Furthermore, the influence of dispersion upon the emission coefficient is taken into account; some relations for the region of dispersion are given.     

Dependence of the Intensity of the Spectral Lines and the Composition of the Sample and the Plasma Parameters of the Unipolar Arc

The investigation was made of the dependence of the intensity of Tl, Ga, Mo, Mg, Mn, Sn, Bi, Ni, Zn, Pt and Au spectral lines and the plasma parameters (temperature T, electron concentration n_e, degree of 6 ionnization α) from concentration of lithium additive.     

Extracting the wavefunction of the LSP at the LHC

We consider associated production of squarks and gluinos with the lightest supersymmetric particle (LSP), or states nearly degenerate in mass with it. Though sub-dominant to pair production of color SU(3)-charged superpartners, these processes are directly sensitive to the wavefunction composition of the lightest neutralinos. Exploiting event-shape variables - including some introduced here for the first time - we are able to identify the composition of the LSP by selecting events involving a single high-pT jet recoiling against missing transverse energy. We illustrate the proposed technique on a set of benchmark cases and propose methods for applying these results in more realistic experimental environments.     

Set the controls for the heart of the Sun

In this paper we describe experiments conducted with high-power lasers that are attempting to replicate, for a very short time and in miniature, conditions found in the Sun. Experiments to date have reached conditions in the outer part of the Sun. To reach the Sun's centre requires compression of material to very much greater than solid density and heating to over ten million degrees. To achieve this, a new class of experiments and a new generation of high-power lasers are required.     

On the Question of the Source of the Apokamp

Technical Physics - The object of this work is the apokamp—a new type of plasma jet, which is formed from a bright offshoot emerging at the bending point of a channel of a high-voltage...