Reijnders M P, van Kruisbergen P A, Taban G, van der Geer S B, Mutsaers P H A, Vredenbregt E J D, Luiten O J
Department of Applied Physics, Eindhoven University of Technology, P.O Box 513, 5600 MB Eindhoven, The Netherlands.
Phys Rev Lett. 2009 Jan 23;102(3):034802. doi: 10.1103/PhysRevLett.102.034802. Epub 2009 Jan 22.
We present time-of-flight measurements of the longitudinal energy spread of pulsed ultracold ion beams, produced by near-threshold ionization of rubidium atoms captured in a magneto-optical atom trap. Well-defined pulsed beams have been produced with energies of only 1 eV and a root-mean-square energy spread as low as 0.02 eV, 2 orders of magnitude lower than the state-of-the-art gallium liquid-metal ion source. The low energy spread is important for focused ion beam technology because it enables milling and ion-beam-induced deposition at sub-nm length scales with many ionic species, both light and heavy. In addition, we show that the slowly moving, low-energy-spread ion bunches are ideal for studying intricate space charge effects in pulsed beams. As an example, we present a detailed study of the transition from space charge dominated dynamics to ballistic motion.
我们展示了对脉冲超冷离子束纵向能量展宽的飞行时间测量结果，这些离子束由捕获在磁光原子阱中的铷原子的近阈值电离产生。已经产生了定义明确的脉冲束，其能量仅为1 eV，均方根能量展宽低至0.02 eV，比最先进的镓液态金属离子源低2个数量级。低能量展宽对于聚焦离子束技术很重要，因为它能够在亚纳米长度尺度上对多种离子种类（包括轻离子和重离子）进行铣削和离子束诱导沉积。此外，我们表明，缓慢移动、低能量展宽的离子束团对于研究脉冲束中复杂的空间电荷效应是理想的。作为一个例子，我们对从空间电荷主导的动力学向弹道运动的转变进行了详细研究。
