Search for anomalous interaction mean free paths of charge, 2≦Z≦18 projectile fragments in emulsions exposed to 1.8 A GeV40Ar ions

⁴⁰Ar-emulsion interactions are studied, to investigate the question of anomalons, in twoG- 5 emulsion stacks. In about 4600 primary interactions, projectile fragments of Z≧2 for all generations have been followed until they interact or leave the stack. After careful estimation of charges of these fragments, variation of their mean free paths is studied as a function of distance from the preceding interaction. Generation effect,N _h dependence and production angle effect are investigated. In addition multi-chain events are analysed separately. Our results do not show anomalons at the 6% level and are consistent with non-occurrence of anomalons. However, this experiment is not sensitive enough to rule out anomalons (with a mfp of the order of 2 to 3 cm) produced at about 1% (or less) level.     

Possible evidence for a narrow isovectorB=2 resonance below pion production threshold

Some evidence is presented for a narrow peak at 1969±2 MeV (FWHM=9±2 MeV) in the missing mass spectrum of the³He(p, d) reaction, with 3 standard deviations. The nature of this state, the mass of which is below the NN threshold, is discussed in connection with structures found in other experiments.     

Virtual miscibility gap and interdiffusion coefficient in iron-nickel invar alloys

Fe-Ni Invar alloys exhibit anomalies in thermodynamic and physical properties at high temperatures. This is considered to result from the tendency to two-phase separation in the fcc phase. This idea is supported also by interdiffusion experiments in the Fe-Ni system, where the interdiffusion coefficient is anomalously small in the Invar region at lower temperatures. A simple theory of regular solutions based on a pair interaction model is applied to the Fe-Ni system; with the assumption of two gamma states this gives a miscibility gap in the Invar region.     

Analysis of two neutron (proton) transfer reaction data in the Zr-region

The spectroscopic amplitudes, form factors, angular distributions and total cross-sections for two nucleon transfer reactions in Zr-region in the zero range distorted wave Born approximation are calculated using consistent set of shell model wave functions. A single normalisation factor gives a good fit to all the two neutron transfer reaction data whereas the corresponding fit for the two-proton transfer reaction data is less satisfactory.     

μ+ depolarization inAlGd alloys

The ⁺ depolarization rate in diluteAlGd alloys containing 50 and 450 atomic ppm Gd was measured in a transverse field of 80 Oe over the temperature range 6–300 K. For both alloys, A increased dramatically above 200 K, reaching values of 0.69 and 0.93 s^–1, respectively, near room temperature. The results are interpreted as providing evidence for a thermally-activated trapping mechanism.This work was supported by the U.S. Department of Energy.     

Nonlinear mixing of oppositely travelling surface plasmons

A theoretical treatment of the nonlinear mixing of two contra-directional surface plasmons of frequency ω₁ and ω₂ propagating on a semi-infinite metal surface is presented. The nonlinear interaction is analysed in terms of (a) nonlinear surface currents due to the breaking of inversion symmetry and the rapid variation of the normal electric field component at the surface, and (b) the nonlinear response of the electron gas in the bulk of the metal. These currents are treated as source terms for Maxwell's equations and electromagnetic fields are found which satisfy the driven wave equation and boundary conditions at the frequencies ω₁ ± ω₂. At the difference frequency ω₁ ? ω₂ the solution fields decay exponentially into both the air and the metal. However, at the sum frequency ω₁ + ω₂, coupling to transverse electromagnetic waves in both the air and the metal is predicted under appropriate wavevector and frequency conditions. The free-space radiation field is treated in detail and the feasibility of its experimental detection is discussed. No coupling to longitudinal bulk plasmons is predicted in this model of the nonlinear interaction.     

A note on the radiation impedance of a circumferential slit in a circular cylinder

The modal radiation impedance of a circumferential opening in a circular cylinder is obtained as a simple integral formula. Calculation results are presented, demonstrating the effects of the width/radius ratio of the opening.     

Sound propagation and radiation through a vaneless diffuser

A simple analysis has been carried out to examine acoustic effects of attaching to the termination of an annular duct a vaneless diffuser through which incident plane waves propagate and radiate out circumferentially. The results are shown in the form of a reflection coefficient which expresses the ration of the incident and reflected waves at the diffuser inlet.     

一种非接触式稀土荧光自参比温度传感器

发展了一种非接触式稀土荧光自参比温度传感器,即将有机稀土配合物K[Yb(Az)₄]包埋在苯乙烯-甲基丙烯酸甲酯共聚物中,并附着在洁净的石英片上制备得到了温度传感薄膜Yb@PSMM。通过研究不同温度下Yb3+的荧光发射光谱,利用其在近红外波段荧光性质随温度变化的规律,开发了一种比率型稀土荧光温度传感方法,其原理是通过不同温度下Yb3+的荧光发射光谱的形状随温度的变化,结合在不同温度下Yb3+的核外电子在外层Stark劈裂亚能级上的分布符合Boltzmann分布律的特点,利用其近红外荧光发射光谱中900 nm~990 nm波长范围内与990~1 150 nm波长范围内的积分峰面积比的自然对数与温度的倒数呈现的线性关系作为温度测量的标准曲线,实现了-195~105 ℃范围内的温度精确测量。经考察,该发光温度传感器在0 ℃附近的温度测量分辨率达到了0.1 ℃。与已报道的发光温度传感器相比,提出的新型温度传感器具有如下几个优势：其一,所选用的发光材料的Stokes位移大于500 nm,有效地避免了环境背景干扰;其二,由于采用荧光积分峰面积而非荧光强度作为考察对象,大大减小了测量中由于仪器或测量次数较少引入的随机误差;其三,采用同一发光材料的荧光发射光谱中两个荧光峰面积的比值,相当于在体系中引入了自参比,有效避免了由于荧光材料的浓度、几何构型以及光源强度等外界因素变化对测量结果产生的影响;其四,利用稀土发光材料作为温度传感材料,可以利用其荧光寿命长、单色性好、强度高的特点;其五,温度传感膜本身不溶于水,也不在水中扩散,便于直接测量原位温度变化;其六,Yb3+的发光位于900~1 150 nm的近红外波长范围,而这个波段的荧光具有较好的穿透性使得该温度传感器有望在复杂体系的温度传感、成像等领域发挥重要作用。在实际测量的装置中,通过调整光路使得辐照在样品上的入射光斑大小仅约为1 mm2,并将Yb@PSMM固体膜样品的放置方向与入射激发光的夹角设置为225°,从而规避了入射光源的反射光对检测器的影响,而具有较好穿透能力的近红外荧光几乎不受影响,从而进一步确保了该温度传感器的测量结果。