2013年 6 月 11-14 日，我参加了在丹麦科学院举办的纪念玻尔原子模型 100 周年的科学史会议 （ http://www.nba.nbi.dk/bohratom100yrs.html ）。这里贴出的是我发表在会议文集中的文章。 Shan Gao - Bohratom100.pdf How do electrons move in atoms? From the Bohr model to quantum mechanics Niels Bohr proposed what is now called the Bohr model of the atom in 1913. He suggested that electrons are particles and they undergo two kinds of motion in atoms;they either move continuously around the nucleus in certain stationary orbitsor discontinuously jump between these orbits. The Bohr model was latterlyreplaced by quantum mechanics in 1925-26, in which the physical state of anelectron is described by a wave function. What, then, does the wave functiontruly represent? Exactly what are electrons? And how do they move in atoms? In this talk, I will show that a deep analysis of protective measurements and the mass and charge distributions of a quantum system may provide the answers. It turns out that microscopic particles such as electrons are indeed particles,but their motion is never continuous but always discontinuous and random. Moreover, the wave function represents the state of random discontinuous motionof particles, and in particular, the modulus square of the wave function givesthe probability density for particles being in certain locations. In some sense, this new picture of quantum reality may be regarded as an extension to Bohr’s discontinuous quantum jumps.
这部获得吉尼斯认证的电影名为《A Boy and His Atom》，采用数千个精确放置的原子制作了近250帧的定格动画动作，由I BM研究院出品。 土豆网链接： http://www.tudou.com/programs/view/UdB87CEXvpM/ 报道链接： http://news.mydrivers.com/1/262/262059.htm 众所周知，原子是化学反应的基本微粒，直径的数量级大约是10^-10m，而且质量极小。有关原子的研究从17世纪就已开始，虽然后来科学家通过实验证实了原子的真实存在，但直到去年7月份，科学家才首次通过超高速摄像机捕捉到单个原子的影像，可见“想见原子一面”难度之高。 不过，IBM近日的一段成果堪称奇迹， 他们竟然用原子拍出了一部“全球最小电影”：《A Boy And His Atom（男孩和他的原子）》，这应该算是最极端的微距镜头了吧 。 据悉，为了完成这部影片， IBM使用他们自制的重达两吨的显微镜在零下268℃的环境下拍摄。通过特殊的控制探针来摆放原子的位置，每摆放一次就形成定格影像，最终合成一部242帧的微型影片 。由于技术细节上过于专业，IBM也并未过多介绍。 只知道制作这部影片的团队之前在电磁存储领域曾有所建树，这部影片算是他们进军“电影界”交上的处女作。
原子的电子亲和能是指在0.0K下的气相中，原子和电子反应生成负离子时所释放的能量。 原子的电子亲和能 Electron Affinities of Atoms 原子序数 (Atomic number) 元素符号(Symbol) E(eV) 原子序数 (Atomic number) 元素符号(Symbol) E(eV) 1 D 0.754593 38 Sr 0.11 H 0.754195 39 Y 0.307 0.754209 40 Zr 0.426 2 He - 41 Nb 0.893 3 Li 0.6180 42 Mo 0.746 4 Be - 43 Tc 0.55 5 B 0.277 44 Ru 1.05 6 C 1.2629 45 Rh 1.137 7 N - 46 Pd 0.557 8 O 1.4611103 47 Ag 1.302 9 F 3.401190 48 Cd - 10 Ne - 49 In 0.3 11 Na 0.547926 50 Sn 1.112 12 Mg - 51 Sb 1.07 13 Al 0.441 52 Te 1.9708 14 Si 1.385 53 I 3.059038 15 P 0.7465 54 Xe - 16 S 2.077104 55 Cs 0.471626 17 Cl 3.61269 56 Ba 0.15 18 Ar - 57 La 0.5 19 K 0.50147 58～71 Ce～Lu - 20 Ca 0.0184 72 Hf 0 21 Sc 0.188 73 Ta 0.322 22 Ti 0.079 74 W 0.851 23 V 0.525 75 Re 0.15 24 Cr 0.666 76 Os 1.1 25 Mn - 77 Ir 1.565 26 Fe 0.151 78 Pt 2.128 27 Co 0.662 79 Au 2.30863 28 Ni 1.156 80 Hg - 29 Cu 1.235 81 Tl 0.2 30 Zn - 82 Pb 0.364 31 Ga 0.3 83 Bi 0.946 32 Ge 1.233 84 Po 1.9 33 As 0.81 85 At 2.8 34 Se 2.020670 86 Rn - 35 Br 3.363590 87 Fr 0.46 36 Kr - 88 Ra - 37 Rb 0.48592 89～103 Ac～Lr -
邱荣涛 2009年11月26日下午4：3018教学楼405 The intensity gradients of inhomogeneous laser-light fields impose ponderomotive forces on charged particles. Such forces have been used to trap and manipulate ions, diffract electrons, and generate charge waves in plasmas. But they were thought to act only very weakly on neutral atomshaving to rely on the polarizability of an atoms charge distribution. Now, however, a group at the Max Born Institute in Berlin has reported the use of intense ultrashort laser pulses to accelerate neutral helium atoms for about 100 femtoseconds at 10 15 m/s 2 . Thats eight orders of magnitude greater than the acceleration (or deceleration) one can get with the continuous-wave techniques used in laser cooling of neutral atoms. The ponderomotive force of an inhomogeneous light field pushes a charged particle toward lower light intensity with a force proportional to the square of its chargeirrespective of signand inversely proportional to its mass. The Berlin group argues that the strong laser pulse excites an electron to the outer reaches of the helium atom where it quivers in the oscillating light field and experiences the ponderomotive force almost as a free electron would. But still bound to the atoms ionic core, it tugs the much heavier core with it away from the laser beams focus. The figure shows how the maximum velocity thus acquired by neutral atoms in the Berlin experiment increases with pulse duration. The dashed curves show the theoretical expectation for the groups model of electron excitation and the consequent ponderomotive force. Such ultrastrong acceleration of neutral atoms, they suggest, could be exploited for atomic-beam optics, atom deposition, and controlled chemical reactions. 附件中是相关文章 Acceleration of neutral atoms in strong short-puls
小道消息： Accelerating neutral atoms （邱荣涛） The intensity gradients of inhomogeneous laser-light fields impose ponderomotive forces on charged particles. Such forces have been used to trap and manipulate ions, diffract electrons, and generate charge waves in plasmas. But they were thought to act only very weakly on neutral atomshaving to rely on the polarizability of an atoms charge distribution. Now, however, a group at the Max Born Institute in Berlin has reported the use of intense ultrashort laser pulses to accelerate neutral helium atoms for about 100 femtoseconds at 10 15 m/s 2 . Thats eight orders of magnitude greater than the acceleration (or deceleration) one can get with the continuous-wave techniques used in laser cooling of neutral atoms. The ponderomotive force of an inhomogeneous light field pushes a charged particle toward lower light intensity with a force proportional to the square of its chargeirrespective of signand inversely proportional to its mass. The Berlin group argues that the strong laser pulse excites an electron to the outer reaches of the helium atom where it quivers in the oscillating light field and experiences the ponderomotive force almost as a free electron would. But still bound to the atoms ionic core, it tugs the much heavier core with it away from the laser beams focus. The figure shows how the maximum velocity thus acquired by neutral atoms in the Berlin experiment increases with pulse duration. The dashed curves show the theoretical expectation for the groups model of electron excitation and the consequent ponderomotive force. Such ultrastrong acceleration of neutral atoms, they suggest, could be exploited for atomic-beam optics, atom deposition, and controlled chemical reactions. 参考文献：U. Eichmann et al., Nature 461 , 1261, 2009 .
标签: 原子
