New search for processes violating the Pauli exclusion principle in sodium and in iodine

In this paper a new search for non-Paulian nuclear processes, i.e. processes normally forbidden by the Pauli Exclusion Principle (PEP), is presented. It has been carried out at the Gran Sasso National Laboratory of the INFN by means of the highly radiopure DAMA/LIBRA set-up (sensitive mass of about 250 kg highly radiopure NaI(Tl)). In particular, a new improved upper limit for the spontaneous non-Paulian emission rate of protons with energy E _p ≥ 10 MeV in ²³Na and ¹²⁷I has been obtained: 1.63 × 10⁻³³ s⁻¹ (90% C.L.). The corresponding limit on the relative strength (δ ²) for the searched non-Paulian transition is δ ²≲(3–4)×10⁻⁵⁵ (90% C.L.). Moreover, PEP-violating electron transitions in iodine atoms have also been investigated. Lifetimes shorter than 4.7×10³⁰ s are excluded at 90% C.L.; this allows us to derive the limit δ _e ²<1.28×10⁻⁴⁷ (90% C.L.). This latter limit can also be related to a possible finite size of the electron in composite models of quarks and leptons providing superficial violation of the PEP; the obtained upper limit on the electron size is r ₀<5.7×10⁻¹⁸ cm (energy scale of E≳3.5 TeV).     

铁磁材料动态磁滞回线测绘方法的优化设计

文中介绍一种涉及铁磁材料动态磁滞回线测绘方法的优化设计.该设计能观察和测绘硬、软磁样品的动态磁滞回线,观察、测绘速度快,方法简便,检测有关数据较准确.     

电场中Eu原子电离阈移动的实验研究

提出了一种新方法, 精确确定了稀土Eu原子第一电离阈的位置. 先用脉冲电场对Eu原子的高激发Rydberg态进行延时场电离探测, 再通过反向静电场排除光电离和自电离等其他路径所产生的离子信号的干扰, 观察并研究了Eu原子第一电离阈随着电场移动的规律. 由此所确定的零场下第一电离阈的数值与采用其他方法所确定的文献值^{[1, 2]}相一致, 从而验证了该方法的可靠性.     

高功率固体激光器锥形空间滤波孔应用

锥形空间滤波孔是一种应用于高功率固体激光装置空间滤波的新型结构滤波小孔,其内部光滑的锥形结构可以有效滤除光束中的高频成分且避免等离子堵孔现象的发生。根据神光-Ⅲ主机装置结构特点,设计并加工了适用于主机装置的锥形空间滤波小孔,并开展了应用实验研究。通过与传统的平面结构滤波小孔对比可以看出,锥形小孔有效地避免了等离子体度堵孔现象,在与光束波前补偿技术配合使用条件下,保证光束顺利过孔,并成功实现了基频光7988 J的满能量输出。     

利用自电离探测技术研究Sm原子Rydberg态光谱

采用孤立实激发与自电离探测技术相结合的方法对Sm原子偶宇称高激发态进行了系统研究.按照不同的自电离通道将所测数据进行了分类和比较,并进行了详细讨论.不仅报道了许多收敛于不同电离限的Rydberg态的能级位置和跃迁的相对强度等信息,而且还把处于同一能域内的Rydberg态和价态进行了辨识.另外,不但提供了一种有效识别不同类型的高激发态的鉴别技术,而且还对处于41800 cm^-1到43800 cm^-1能域内的Rydberg态和价态的光谱特性进行了详细分析和讨论. 关键词： 自电离探测 Rydberg态 Sm原子     

Synthesis of broadband and flat parametric gain by idler loss in optical fiber

Besides dispersion engineering, idler-band distributed fiber loss provides a new synthesis freedom to flatten and broaden the gain spectrum for a fiber-optic parametric amplifier. This interesting phenomenon is based on the fact that the power balance between signal and idler is broken by idler loss, which changes the power conversion process in four-wave-mixing. The pump-to-signal conversion efficiency is kept unchanged in spite of the loss.     

枝晶生长和气泡形成的数值模拟

本文建立了二维的格子玻尔兹曼方法-元胞自动机(lattice Boltzmann method-cellular automaton, LBM-CA)耦合模型, 对凝固过程中枝晶生长和气泡形成进行模拟研究. 本模型采用CA方法模拟枝晶的生长, 根据界面溶质平衡法计算枝晶生长的驱动力. 采用基于Shan-Chen多相流的LBM模拟气泡在液相中的生长和运动. 在LBM-CA的耦合模型中包含了固-液-气三相之间的相互作用. 应用Laplace定理和模拟气-液-固三相之间的润湿现象对模型进行了验证. 应用所建立的LBM-CA耦合模型模拟研究了气-液相互作用系数对单气泡生长的影响. 发现单气泡的生长速度和平衡半径随气-液相互作用系数的增大而增大. 定向凝固过程中枝晶和气泡生长的模拟结果再现了枝晶的择优生长、 气泡的优先形核位置、气泡的长大、合并、在枝晶间受挤变形以及在液相通道中的运动等物理现象, 与实验结果符合良好. 此外, 初始气体含量越高, 凝固结束时气泡的体积分数也相对较高. 本模型的模拟结果可以揭示在凝固过程中气泡形核、 生长和运动演化以及与枝晶生长相互作用的物理机理.     

移动Ad Hoc网络动力学同步能力的研究

研究了移动Ad Hoc网络的动力学同步行为.用特征值比R来衡量网络的同步能力,特征值比R越小,同步能力越强.结果表明最初该网络的特征值比R随聚类系数C的增加而增加,继续增大聚类系数,特征值比反而减小.特征值比随聚类系数并不是普遍的正比关系也不是反比关系,而是先增大后减小,明显存在一个极值.     

Tip-enhanced Raman scattering: Influence of the tip-surface geometry on optical resonance and enhancement

The tip-sample distance (z) dependence of tip-enhanced Raman scattering (TERS) has been investigated. The intensities of both, the Raman lines and the broad TERS background, exhibit strong decays with increasing z, which are nearly complete within 10 nm withdrawal of the STM tip in z direction. Interestingly, the maximum of the broad Lorentzian-shaped TER background is substantially blue shifted in energy with z. This effect is ascribed to a corresponding blue shift of the energies of localized plasmon modes upon tip retraction. Both experimental results fit very well data of a simple theoretical near-field model.     

Experimental study of the time-resolved reflectivity of chromium film

The transient time-resolved reflectivity of chromium film is studied by femtosecond pump-probe technique with a 70-fs laser. Experimental results show that the reflectivity change increases with the power of the pump laser. The fast decrease of the reflectivity occurs between 0-200 fs which is mainly due to the electron-electron interaction. Subsequencely, the slower recovery of the reflectivity between 200-900 fs is mainly due to the electron-phonon coupling process. The reflectivity after 900 fs rises little to a near-constant value for the thermal equilibrium of the system. The experimental results can be explained properly with numerical simulation of the two-temperature model. It is helpful for understanding of the electron ultrafast dynamics in chromium film.