High resolution laser spectroscopy of small gas-phase metal-ligand molecules

该研究项目旨在利用激光光谱学来理解小的气相金属配体分子的基本结构和性质。分子通过各种方法产生，用激光激发到高能态，然后通过发光从高能态衰减回低能级。通过探测发射的光或观察分子吸收辐射的能量，可以对分子中的键合、结构和相互作用有详细的了解。例如，这些信息对于理解发生在大气、空间以及任何表面化学或催化过程中的化学和物理过程都很重要。这些分子是在冷分子束（定义明确的分子流）中产生的，以提供高度分辨和简化的光谱。在实验中，高功率激光聚焦在脉冲气体喷嘴前的金属目标上。来自目标的汽化原子与从喷嘴流出的气体中的试剂发生反应。然后气体通过一个小孔膨胀进入真空系统，产生光束。分子用可调谐激光探测下游，分子吸收作为频率的函数被观察到。研究的目标分子有三组：A)双原子金属配体物种（dml）， B)小金属配体多原子物种（MLPs）， C)半导体物种（ss）。我们正在测量一些dml （RhF, RhCl, HfF，…），这些分子的吸收是第一次被观察到，以全面研究键合特征，并为某些催化和天体物理学感兴趣的分子提供光谱信息。在众多mlp中，我们对金属单羰基感兴趣。这些在表面化学和催化反应中具有重要意义的物质的气相研究很少。我们将首次对这些物种进行研究，以提供有关其特性的新信息。我们最近研究了一种重要的半导体物质，GeH2。我们将继续研究在半导体电子器件制造中其他重要的SSs。

This research program is geared towards understanding the fundamental structure and properties of small, gas-phase, metal-ligand molecules using laser spectroscopy. The molecules are produced by various methods and excited with a laser to higher energy states from which they can decay back to lower energy levels by emitting light. By detecting either this emitted light or observing at which energy the molecules absorb the radiation, a detailed understanding of the bonding, structure and interactions in the molecules can be gained. This information is important, for example, in understanding both the chemical and physical processes occurring in the atmosphere, in space, and in any surface chemistry or catalytic process.   The molecules are produced in cold molecular beams (well defined streams of molecules) to give highly resolved and simplified spectra. In the experiments, a high power laser is focussed onto a metal target held in front of a pulsed gas nozzle. Vaporized atoms from the target react with a reagent in the gas flowing from the nozzle. The gases then expand through a small hole into a vacuum system creating the beam. The molecules are probed downstream with a tunable laser and molecular absorptions are observed as a function of frequency.   Three groups of molecules are targeted in the research: A) diatomic metal-ligand species (DMLs), B) small metal-ligand polyatomics (MLPs), and C) semiconductor species (SSs). We are measuring a number of DMLs (RhF, RhCl, HfF, ...), where absorptions for these molecules are being observed for the first time, to comprehensively study the bonding characteristics and provide spectral information for certain molecules of catalytic and astrophysical interest. Of the many MLPs, we are interested in metal monocarbonyls. Few gas-phase studies of these species, which are important in surface chemistry and catalytic reactions, exist. We will examine these species for the first time to provide new information on their properties. We recently studied an important semiconductor species, GeH2. We will continue our studies by looking at other SSs of importance in the fabrication of semiconductor electronic devices.