Quantum reflection from a solid surface at normal incidence

We observed quantum reflection of ultracold atoms from the attractive potential of a solid surface. Extremely dilute Bose-Einstein condensates of 23Na, with peak density 10(11)-10(12) atoms/cm(3), confined in a weak gravitomagnetic trap were normally incident on a silicon surface. Reflection probabilities of up to 20% were observed for incident velocities of 1-8 mm/s. The velocity dependence agrees qualitatively with the prediction for quantum reflection from the attractive Casimir-Polder potential. Atoms confined in a harmonic trap divided in half by a solid surface exhibited extended lifetime due to quantum reflection from the surface, implying a reflection probability above 50%.     

Specular reflection of very slow metastable neon atoms from a solid surface

An ultracold narrow atomic beam of metastable neon in the 1s3[(2s)(5)3p:1P0] state is used to study specular reflection of atoms from a solid surface at extremely slow incident velocity. The reflectivity on a silicon (1,0,0) surface and a BK7 glass surface is measured at the normal incident velocity between 1 mm/s and 3 cm/s. The reflectivity above 30% is observed at about 1 mm/s. The observed velocity dependence is explained semiquantitatively by the quantum reflection that is caused by the attractive Casimir-van der Waals potential of the atom-surface interaction.     

Anomalous microwave reflection from a metal surface induced by spoof surface plasmon

The reflection of X-band microwaves (8-12 GHz) from a metallic aluminum (Al) surface with groove grating corrugations was investigated experimentally. It was shown that the reflection of p-polarization is much less than the microwave reflected from the corresponding area of an unruled Al surface, with selective wavelength. The experimental results demonstrated that the anomalous microwave reflection is strongly associated with the excitation of spoof surface plasmons at the Al-air interface by the surface grating coupler. This near-total absence of reflected microwaves is similar to the famous Wood's anomaly in the optical regime and is of fundamental importance to the applications of spoof surface plasmons in the microwave regime.     

反质子物理

本文介绍反质子与核子和与原子核碰撞后各种物理现象．它与核子的散射获得的位势是吸引势和吸收型,与核的光学势是强吸收到．湮没后产生众多的介子和重子．以及在高能下湮没产生奇特性粒子、带粲的介子、重子．并探索获得混杂子、在核中存在反质子、其它新粒子的可能性． In this paper several physical phenomena of antiproton-nucleon and antiproton-necleus collision are discussed. The potential obtained from p-N scattering is attraction and absorption type. The optical potential of nucleus is strong absorption type. The annihilation happens after pp collision and thenproduces many kinds of meson, hadron, even produce some exotic particle and charmonium at high energy pp anihilation. Posibilities to find hybrids, antiproton and other particles in nucleus are also explored.     

暗物质粒子湮没生成的反质子谱

在粒子物理最小超对称标准模型下,计算了X0X0→gg物理过程的反应截面.利用所获得的截面值给出了暗物质粒子Neutralino X0湮没生成的反质子谱.计算表明:反质子谱具有的可观性,为寻找暗物质粒子和超对称粒子提供了一种可能的途径.     

Antiproton induced reactions

The various aspects of antiproton physics are shortly reviewed, and its relevance for the possible discovery of new particles and effects is pointed out. Then a survey of the nucleon-antinucleon interactions is given. In the nucleon-antinucleon annihilations, there is a big amount of experimental data that call for theoretical explanation. Importance of specific spin and isospin channels for our understanding of antiproton physics is stressed.Lecture presented at the Indian-Summer School on Interaction in Hadronic Systems, Praha (The Czech Republic), 25–31 August 1993.     

Antiproton annihilation as a deconfinement process

N¯N annihilation into mesons through the deconfinement stage is analysed. Behaviour of deconfined quark-gluon plasma describes an equation of state, with first order quark and gluon interactions. The effects of pion structure and threshold irregularities are considered.Invited talk to the symposium Mesons and Light Nuclei IV, Bechyn, Czechoslovakia, September 5–10, 1988.     

Quantum features of reflection of relativistic particles by a crystal surface

A new mechanism of reflection of relativistic particles by a crystal surface at grazing angles is considered. The reflection takes place when the “transverse” energy value (connected with the particle motion perpendicular to the surface) lies in the forbidden band of the energy spectrum in a one-dimensional periodic potential which is the sum of continuous potentials of crystallographic planes being parallel to the surface.     

Antiproton intensity limitations

The recent developments on antiproton rings are reviewed. They cover the new focusing methods used in the vicinity of the production targert, various functions of a collector and the way they are implemented, the accumulation and the intensity limitations.     

Antiproton annihilation spectra

Recent data on antiproton (antineutron) spectra from hydrogen, deuterium and nuclear targets are discussed. Special emphasis is given to rare or unusual channels and phenomena. Work supported in part by the Air Force Office of Scientific Research, Air Force Systems Command, USAF under grant AF05R87-0246 and U.S. National Science Foundation.     

Multiple reflection effect inside a hemispherical solid immersion lens

The reflection inside a hemispherical solid immersion lens (h-SIL) is analyzed by using the film-interference optics and the new unique characteristic of the h-SIL is presented. The image theory of SIL microscopy is developed. Numerical results show that the reflection inside the h-SIL, especially for large mismatch in refractive indices between the SIL and the medium, has an important influence on the resolution of SIL surface microscope and the collection efficiency from the emitter. Theoretical and experimental results are compared through three examples, the reflection-mode microscope, the transmission-mode microscope, and the collection of light from the emitters. The present theoretical values are quite consistent with the experimental values in SIL microscopy. It is of interest to note that owing to the interference in the SIL, the resolution and collection efficiency periodically oscillate with the radius of an h-SIL, which mean that the radius of an h-SIL has to be well-controlled to achieve enough high resolution and collection efficiency.     

Resonance fluctuation-electromagnetic energy losses during the glancing reflection of a neutral atomic beam from the smooth amorphous surface of a solid

The energy losses of a Cs⁺ion beam are theoretically studied during its glancing reflection from a smooth amorphous surface of a dielectric or a semiconductor and films made of these materials on a metallic substrate. The conditions of resonance fluctuation-electromagnetic interaction between neutralized Cs atoms and surface polaritons are considered for surfaces where the effects of interest seem to be the most significant. Calculations indicate that, at the optimized initial glancing angle and the Cs⁺ ion beam energy (ψ_in = 0.1–1.0 mrad, E ₀ ～ 50–100 keV), the fluctuation-electromagnetic forces substantially contribute to the total energy losses and this contribution has characteristic dependences on the temperature, particle velocity, and material parameters.     

Acoustic field imaging by light reflection at the free surface of a liquid

In this paper we present a novel technique for acoustic field imaging. This technique is based on reflection of a collimated laser beam at the free surface of a liquid. The reflected beam becomes phase modulated by the acoustic wave as in acoustical holographic systems. We do not use a reference acoustical beam for holographic reconstruction but we observe this phase modulation using dark-field techniques. It gives a measurement of the acoustic field power as a function of the position. The authors have built an optical imaging system and carried out experiments with piezocomposite transducers. The technique presented in this work is able to give fast quantitative information about the performance of individual ceramic rods of the piezocomposite.