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

这项研究计划旨在利用激光光谱学来了解气相金属配体小分子的基本结构和性质。分子是通过各种方法产生的，并用激光激发到更高的能量状态，从这些状态它们可以通过发光衰减回较低的能级。通过检测这种发射的光或观察分子吸收辐射的能量，可以详细了解分子中的成键、结构和相互作用。例如，这些信息对于理解大气、空间以及任何表面化学或催化过程中发生的化学和物理过程都很重要。因此，分子是在冷分子束(定义良好的分子流)中产生的，以提供高度分辨率和简化的光谱。在实验中，高功率激光聚焦在脉冲气体喷嘴前面的金属靶上。靶上蒸发的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，产生束流。用可调谐激光探测下游的分子，观察到分子吸收是频率的函数。以下三组分子是研究的目标：A)双原子金属-配体物种(DMLS)，B)小金属-配体多原子(MLP)，以及C)半导体物种(SSS)。我们正在测量一些DML(RHF，RhCl，HFF，...)，其中对这些分子的吸收是首次观察到的，以全面研究成键特性，并提供某些具有催化和天体物理兴趣的分子的光谱信息。在众多的MLP中，我们对金属单羰基感兴趣。在表面化学和催化反应中很重要的这些物种的气相研究很少。我们将首次研究这些物种，以提供有关它们特性的新信息。我们最近研究了一种重要的半导体物种GeH2。我们将继续我们的研究，寻找其他在半导体电子器件制造中具有重要意义的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.