Instrument Development: a High Density Source of Cold, Slow Molecules

本项目由化学学部化学测量与成像项目资助。德州农工大学的Dudley Herschbach和Igor Lyuksyutov试图开发一种能够以低至5米/秒（基准）的速度传输密度高达1012cm -3的冷分子光束的仪器。该仪器是一个脉冲，反向旋转超音速源（PCRS），任何分子可用的气体可以减速（或加速）。在如此低的速度下，这样的密度比目前通过其他方法获得的密度要大4个数量级。~ 5米/秒的极慢光束对于许多需要捕获分子的实验是必不可少的。预期的光束密度，通常为1010 cm-3，对于使被捕获的分子随后冷却到超冷状态是必不可少的。在另一种不同的模式下，用于碰撞研究，通过将PCRS与同向固定源配对，并通过调整转子转速使光束速度紧密匹配，可以获得非常低的相对动能。这种合并波束的性能具有广泛的适用性。它将打开化学反应动力学的“物质波”或“超量子”领域，在那里碰撞的德布罗意波长远远超过反应物分子的大小。该项目还包括开发一种辅助仪器，适用于具有磁矩的分子。它是一种单级磁性减速机（SSMD），设计用于与PCRS结合运行。SSMD初步版本的计算机模拟表明，只有7厘米长的脉冲场，具有抛物线轮廓和5特斯拉的强度，可以将O2从50米/秒减速到2或3米/秒。组合式pcr + SSMD仪器结构紧凑、坚固、构造和操作简单。这个项目将提供工具，将显著推进实验研究，探索并最终利用非常慢的分子的新特性。据预测，从信息处理（量子计算机）到重力探测器的未来应用将从慢分子技术中出现。这项研究的冒险性质既引起了学生的兴趣，也引起了公众的兴趣。本科生（由REU资助或TAMU资助）以及研究生将做出重大贡献。这项工作涉及设备的设计研究，包括许多桌面组件和实验协议，从而提供计算机模拟和其他实用艺术的经验。两位pi都热衷于教学和指导学生，并致力于改善K-12科学教育和公众对科学的理解。与这个项目直接相关的计划是针对高中生的“德州最酷的地方”暑期项目，以及针对普通大众（包括高中生和中学生）的“超冷世界”和“纳米世界的奇才”系列讲座。

In this project, funded by the Chemical Measurements and Imaging Program of the Chemistry Division, Profs. Dudley Herschbach and Igor Lyuksyutov of Texas A&M University seek to develop an instrument capable of delivering beams of cold molecules with densities up to 1012 cm-3 at speeds as low as 5 m/s (the benchmark). The instrument is a pulsed, counter-rotating supersonic source (PCRS), with which any molecule available as a gas can be slowed (or speeded). Such densities at speeds so low are about four orders of magnitude larger than currently available by other means. Very slow beams of ~ 5 m/s are essential for many experiments that require trapping molecules. Anticipated beam densities, typically 1010 cm-3, are essemtial to enable the trapped molecules to be subsequently cooled down to the ultracold realm. Used in a different mode, for study of collisions, very low relative kinetic energies can be attained by pairing the PCRS with a codirectional stationary source and closely matching the beam velocities by adjusting the rotor speed. This merged-beam capability is widely applicable. It will open up the "matterwave" or "hyperquantum" realm of chemical reaction dynamics, where collisional deBroglie wavelengths much exceed the size of reactant molecules. The project also includes the development of an auxiliary instrument, applicable to molecules with magnetic moments. It is a single-stage magnetic decelerator (SSMD), designed to operate in combination with the PCRS. Computer simulations for a preliminary version of the SSMD demonstrate that a pulsed field only 7 cm long, with parabolic profile and strength 5 Tesla, can decelerate O2 from 50 m/s to 2 or 3 m/s. The combined PCRS + SSMD instrument will be compact, robust, simple to construct and operate.This project will provide tools that will significantly advance experimental research exploring and eventually using the novel properties of very slow molecules. Futuristic applications from information processing (quantum computers) to gravity detectors have been predicted to emerge from slow molecule technology. The adventurous character of the research fosters interest both among students and the wider public. Undergraduate students (supported either by REU funding or by TAMU) as well as graduate students will contribute significantly. The work involves design studies for apparatus, including many table-top components, and experimental protocols, thereby providing experience in computer simulations and other practical arts. Both PIs are evangelical about teaching and mentoring students and have undertaken efforts to improve K-12 science education and public understanding of science. Directly linked to this project are plans for a "Coolest Place in Texas" summer program for high school students and a pair of lecture series "The Ultracold World" and "Wizards of the NanoWorld" for the general public, including high school and middle school students.