Spectroscopic studies of van der Waals interactions, cluster containing transient intermediates, and development of Mid IR nano-sensors

本提案聚焦于分子/化学物理中的三个领域。首先，我们将对原子和分子之间的非共价键进行实验和理论研究。非共价键比化学键弱几个数量级，但作用范围更广，对许多化学和生物系统有着深远的影响。它们负责气体的碰撞效应，气溶胶的形成，水的体积特性，蛋白质的二级和三级结构以及DNA的双螺旋结构等等。非共价相互作用由相互作用分子的电子结构决定，原则上可以用薛定谔方程（SE）来处理。然而，由于电子相关问题，该方程的精确解是不可能的。其最简单的形式是由动能和势能项组成。虽然动能的计算很简单，但PES的计算却是一项艰巨的任务。我们将利用实验和理论之间的协同作用来开发具有越来越高的复杂性和准确性的势能面（PESs）。PES是SE的定义部分，也是分子簇的光谱或动力学研究的基本成分。新兴的高精度PESs可以对我们的光谱观测进行测试。其次，我们对碳氢化合物遥感的线参数和吸收截面形式的实验室数据感兴趣。例如，由于乙烷是第二丰富的碳氢化合物（仅次于甲烷），因此需要实验室数据来研究外行星大气中的甲烷循环。我们数据的其他用途包括传输模拟、工业过程监测和污染监管研究。我们将着重于乙烷中红外波段频率和强度的量子力学模型的发展。然后，可以使用线路参数来计算任意温度和压力下的光谱，以覆盖所遇到的物理条件。最后，中红外包含许多温室气体的强吸收特征，这些特征在传感应用中非常有意义。通过工程硅光子学使光谱传感设备的小型化成为可能，这有可能彻底改变中红外的传感。材料工程的进展表明，硅基光子器件可以支持中红外波段的光传播，其损耗接近电信波段，这使得该区域对纳米级传感器的开发具有吸引力。开发用于无人机的灵敏、小巧、便携、低成本的温室气体监测传感器。拟议研究的结果为群集和气溶胶科学、天文学以及对气候变化、遥感和工业控制过程感兴趣的科学家提出的关键问题提供了答案。

This proposal focuses on three areas in molecular/chemical physics. First, we will conduct experimental and theoretical studies of noncovalent bonds between atoms and molecules. Noncovalent bonds are orders of magnitude weaker than chemical bonds but act over a much longer range and have profound influence over many chemical and biological systems. They are responsible for collisional effects in gases, aerosol formation, bulk properties of water, the secondary and tertiary structures of proteins and the double helix structure of DNA to name a few. Noncovalent interactions are governed by the electronic structure of the interacting molecules which in principle can be treated using the Schrodinger Equation (SE). However, the exact solution to this equation is impossible because of the electron correlation problem. In its simplest form the SE consists of kinetic and potential energy terms. While the kinetic energy is straightforward to calculate, computation of the PES is a nontrivial task. We will use the synergy between experiment and theory to develop potential energy surfaces (PESs) with ever increasing levels of sophistication and accuracy. The PES serves as a defining part of the SE and the essential ingredient for spectroscopic or dynamical study of molecular clusters. The emerging high-accuracy PESs can be tested against our spectroscopic observables. Second, we are interested in laboratory data in the form of line parameters and absorption cross-sections for remote sensing of hydrocarbons. For example, because ethane is the second most abundant hydrocarbon (after methane), laboratory data are required to study the methane cycle in the atmospheres of outer planets. Other uses of our data include transmission simulations, industrial process monitoring, and pollution regulatory studies. We will focus on development of quantum mechanical models for frequency and intensity of the mid-IR bands of ethane. The line parameters can then be used to compute a spectrum at an arbitrary temperature and pressure to cover the physical conditions encountered. Lastly, the mid-IR contains the strong absorption signatures of many greenhouse gases that are of extreme interest in sensing applications. The miniaturization of spectroscopic sensing equipment made possible by engineered silicon photonics has the potential to revolutionize sensing in the mid-IR. Advances in materials engineering have shown that silicon-based photonic devices can support optical propagation in the mid-IR with losses approaching those of the telecommunications band, making the region attractive for nanoscale sensor development. We will develop sensitive, compact, portable, and low-cost sensors for monitoring greenhouse gases to be used on unmanned aerial vehicles. The outcomes of the proposed research hold answers to key questions asked in cluster and aerosol science, in astronomy and by scientists with interest in climate change, remote sensing, and industrial control process.