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11.
Recent experiments suggest that gold single-atom contacts and atomic chains break at applied voltages of 1 to 2 V. In order to understand why current flow affects these defect-free conductors, we have calculated the current-induced forces on atoms in a Au chain between two Au electrodes. These forces are not by themselves sufficient to rupture the chain. However, the current reduces the work to break the chain, which results in a dramatic increase in the probability of thermally activated spontaneous fracture of the chain. This current-induced embrittlement poses a fundamental limit to the current-carrying capacity of atomic wires. 相似文献
12.
建立了超高效液相色谱-电喷雾离子源-串联三重四极杆质谱(UPLC-ESI MS/MS)分析饮用水中高氯酸盐的方法.以300Extend-C18为分析柱,10%甲醇水溶液为流动相,ESI MS/MS串联质谱为检测器,以多重反应监测(MRM)模式监测高氯酸盐m/z 99.5→82.9离子对.方法的线性范围为0.2 ~10 μg/L,相关系数为r2=0.999 9,方法检出限为0.15 μg/L,平均加标回收率为82%,相对标准偏差为4.4%.应用UPLC-ESI MS/MS法测定北京市部分城区饮用水中的高氯酸盐,其中5个水样中检出ClO-4,质量浓度为0.040 ~0.262 μg/L,但在安全阈值范围内,不会对居民健康构成威胁. 相似文献
13.
J. Riedel S. Hoekstra W. Jäger J. J. Gilijamse S. Y. T. van de Meerakker G. Meijer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,65(1-2):161-166
Here we report on the accumulation of ground-state NH molecules in a static magnetic trap. A pulsed supersonic beam of NH (a1Δ) radicals is produced and brought to a near standstill at the center of a quadrupole magnetic trap using a Stark decelerator. There, optical pumping of the metastable NH radicals to the X3Σ? ground state is performed by driving the spin-forbidden A3Π ← a1Δ transition, followed by spontaneous A → X emission. The resulting population in the various rotational levels of the ground state is monitored via laser induced fluorescence detection. A substantial fraction of the ground-state NH molecules stays confined in the several milliKelvin deep magnetic trap. The loading scheme allows one to increase the phase-space density of trapped molecules by accumulating packets from consecutive deceleration cycles in the trap. In the present experiment, accumulation of six packets is demonstrated to result in an overall increase of only slightly over a factor of two, limited by the trap-loss and reloading rates. 相似文献
14.
计算表明,与场的相干态类似的原子相干态,具有不同于场的相干态的压缩行为;进一步证明:直接类比于(?)(ξ)不能得到“原子压缩算符”. 相似文献
15.
A simple high-order Galerkin finite element scheme is formulated to compute both the guided and leaky modes of anisotropic planar waveguides with a diagonal permittivity tensor. Transparent boundary conditions derived from the Sommerfield radiation conditions are used to model the fields at the computational boundaries that allow the radiation into the high index cladding/substrate and decay into the low index cladding/substrate, hence work for both guided and leaky modes. Richardson's extrapolation is employed to achieve high-order accuracy by only using simple first-order-polynomial basis functions. Schemes up to sixth-order of accuracy in the effective index are demonstrated. The resulted non-linear sparse matrix eigenvalue equation is solved using an iterative procedure. The ability of the scheme to compute leaky and guided modes of various structures with isotropic and anisotropic materials, step and graded index profiles is demonstrated; including its applications to investigate the properties of ARROW structures. 相似文献
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The first state selective electron capture cross section measurements at eV energies are reported for collisions between C4+ ions and H2 molecules. The cross sections are measured in a crossed beam experiment by means of Photon Emission Spectroscopy. The ion
beams are decelerated in an octopole ion trap where the trap is used to guide the ion beam through the collision region. The
experimental results are in excellent agreement with previous measurements at higher energies. The 3-state atomic orbital
calculations of Gargaud and McCarroll generally agree with our measurements although there are some discrepancies at lower
energies. However, the results for C4+ are still on a relative scale. To put our measurements on an absolute scale the N4++ H system is investigated at keV energies. These results are in good agreement with the data of previous experiments.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
R. Morgenstern H. Khemliche R. Hoekstra 《Applied Physics A: Materials Science & Processing》1998,67(6):705-710
Received: 27 March 1998/Accepted: 23 October 1998 相似文献
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