Quantum and semiclassical scattering dynamics

量子和半经典散射动力学

• 批准号: 37385-2007
• 负责人: Dumont, Randall
• 金额: $ 0.73万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=361211
• 关键词: Quantum; semiclassical; scattering; dynamics

Advances in nanotechnology are a window into the microscopic realm of electrons, atoms and molecules.  The dynamics, at this level, is quantum mechanical.  There is much to be learned from the computation of exact quantum dynamics for such systems.  Exotic quantum phenomena, without parallel in the familiar classical world, can play a central role - phenomena such as tunneling, nonadiabatic transition and resonance.  Tunneling through an array of barriers gives rise to transmission resonances - peaks in transmission probability to near unity.  Since between resonances, transmission probability is very small, this phenomenon could be the basis for a quantum switch which controls the current of a single electron.  However, a closer look at the transmitting electron reveals that there is a significant chance of it sticking to the barriers, and taking a long time to transmit.  This could limit the performance of the device in an application.  The problem can be overcome by adjusting the barriers - effectively adding an anti-reflection coating to the array - such that the sharp transmission resonances morph into a smooth transmission band exhibiting rapid transmission.  Reflection resonances are also possible.  For example, they arise from avoided crossings between quantum levels associated with motion in directions other than the transmission direction.  We propose to investigate the modification of avoided-crossing arrays in order to blend sharp reflection resonances into smooth reflection bands, with slow reflection replaced by rapid reflection.  In addition to accurate quantum computations, a semiclassical treatment of the dynamics will be provided.  This amounts to a description of the quantum dynamics as the interference of simple waves associated with specific paths across the device - including reflections and interchange of quantum levels.  Other studies address the time development of population inversion in the fluorine + methane chemical laser reaction, and unexpected rates of gas phase organic reactions.  See www.chemistry.mcmaster.ca/dumont/ for more information.

纳米技术的进步是进入电子、原子和分子的微观领域的一扇窗户。在这个层面上，动力学是量子力学的。从对这种系统的精确量子动力学的计算中可以学到很多东西。在熟悉的经典世界中没有平行的奇异量子现象可以发挥核心作用--例如隧穿，非绝热跃迁和共振。通过势垒阵列的调谐引起透射共振-透射概率的峰值接近1。由于在共振之间，透射概率非常小，这种现象可能是量子开关的基础，量子开关可以控制单个电子的电流。然而，仔细观察传输电子会发现，它很有可能会粘在势垒上，并且需要很长的时间来传输。这可能会限制设备在应用中的性能。这个问题可以通过调整屏障来克服-有效地向阵列添加抗反射涂层-使得尖锐的传输谐振变形为表现出快速传输的平滑传输带。反射谐振也是可能的。例如，它们产生于与传输方向以外的方向上的运动相关联的量子能级之间的避免交叉。我们建议研究避免交叉阵列的修改，以便将尖锐的反射共振混合到平滑的反射带中，用快速反射代替缓慢反射。除了精确的量子计算，将提供动力学的半经典处理。这相当于将量子动力学描述为与穿过特定路径相关的简单波的干涉。器件-包括量子能级的反射和交换。其他研究涉及氟+甲烷化学激光反应中粒子数反转的时间发展，以及气相有机反应的意外速率。更多信息请参见www.chemistry.mcmaster.ca/dumont/。