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

点击翻译按钮获取中文摘要

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.