Sheffield L S, Woo S O, Rathnayaka K D D, Lyuksyutov I F, Herschbach D R
Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843, USA.
Rev Sci Instrum. 2016 Jun;87(6):064102. doi: 10.1063/1.4953613.
We describe modifications of a pulsed rotating supersonic beam source that improve performance, particularly increasing the beam density and sharpening the pulse profiles. As well as providing the familiar virtues of a supersonic molecular beam (high intensity, narrowed velocity distribution, and drastic cooling of rotation and vibration), the rotating source enables scanning the translational velocity over a wide range. Thereby, beams of any atom or molecule available as a gas can be slowed or speeded. Using Xe beams in the slowing mode, we have obtained lab speeds down to about 40 ± 5 m/s with density near 10(11) cm(-3) and in the speeding mode lab speeds up to about 660 m/s and density near 10(14) cm(-3). We discuss some congenial applications. Providing low lab speeds can markedly enhance experiments using electric or magnetic fields to deflect, steer, or further slow polar or paramagnetic molecules. The capability to scan molecular speeds facilitates merging velocities with a codirectional partner beam, enabling study of collisions at very low relative kinetic energies, without requiring either beam to be slow.
我们描述了一种脉冲旋转超声束源的改进方法，这些改进提高了性能，特别是增加了束流密度并锐化了脉冲轮廓。除了具备超声分子束常见的优点（高强度、狭窄的速度分布以及转动和振动的剧烈冷却）外，旋转源还能在很宽的范围内扫描平移速度。由此，任何可作为气体使用的原子或分子束都可以被减速或加速。在减速模式下使用氙束，我们已获得实验室速度低至约40±5米/秒、密度接近10¹¹厘米⁻³的结果；在加速模式下，实验室速度高达约660米/秒、密度接近10¹⁴厘米⁻³。我们讨论了一些适宜的应用。提供低实验室速度可以显著增强利用电场或磁场使极性或顺磁性分子偏转、引导或进一步减速的实验。扫描分子速度的能力有助于将速度与同向的伙伴束合并，从而能够研究极低相对动能下的碰撞，而无需任何一束束流速度很慢。
