Research Overview

Molecular Structure and Spectroscopy, Fourier Transform Spectroscopy

Transient SpeciesThe primary objective of our research is the spectroscopicidentification of transient chemical species, especially as they appear in the gas phase. We use high resolution grating spectrographs from the vacuum ultraviolet to the nearinfrared regions of the spectrum, as well as a fourier transform spectrometer.The results of these studies provide fundamental data useful for monitoring the species of interest during chemical reactions, as well as the data necessary for predicting thermodynamic properties. We are especially excited when we can observe a new spectrum and identify for the first time the molecule responsible for it. It's even more fun when this molecule has never been observed by any other experimental technique!Among the systems of current interest are the Group IIIA halides, as seen by absorption and emission spectroscopy between 3500 and 1200Å. We have improved the quality and extent of information about the ground and first two excited states of AlCl, AlBr, GaF, and InCl. We also have observed, for the first time, spectra involving high-lying excited states (Rydberg States) of AlCl, and similar studies are underway for the other molecules in this series. These studies offer intriguing information useful for monitoring the deposition or evaporation of thin metallic films during the manufacturing processes for integrated circuits. They also provide data of potential use in understanding and improving the mechanisms of these supercritical industrial processes.A second area of interest lies in the study of small, gas phase molecules containing H, C, N, and O. HNCN was identified several years ago, but this is the first time it has been practical to provide significant improvements on those initial data. We also have produced and identified for the first time the molecule HCN2 (an isomer of HNCN). Isotopic substitution established the identity of the carrier through its effects on the vibrational structure of an electronic transition near 3100Å. We have analyzed the rotationalstructure of these bands in order to determine the geometric structure of the molecule in two electronic states. An examination of the spectra and mechanisms of formation of these species and other highly reactive species produced under similar conditions (NCN, NCO, and CN) are of particular interest in connection with upper atmosphere chemistry, premordial chemistry leading to the synthesis of amino acids from simple inorganic compounds, and asexamples of isomerization of simple molecules in the gas phase.

Recent Publications

  "An Analysis of the Rotational Structure in theC 1-X1+ Systems of GaF," W. B.Griffith, Jr., G. A. Bickel, H. D. McSwiney, and C. W. Mathews, J. Mol. Spectros., 104, 343 (1984).

  "The Rotational Spectrum of HCNO in Excited Bending Combination States," B. P. Winnewisser, M. Winnewisser, C. W. Mathews, and K. M. T. Yamada, J. Mol. Spectros., 126, 460(1987).

  "Analysis of the 0001 A2+ - 0011 X2 Band of 14NCO and 15NCO," M. Prabhakar, C. W. Mathews,and D. A. Ramsay, J. Mol. Spectros., 130, 419 (1988).

  "The Spectoscopy and Thermochemistry of Na andNa2,"H. D. McSwiney, Darryl W. Peters, William B. Griffith Jr., and C. Weldon Mathews, J. Chem Ed. 66, 857-860 (1990).

  "The v11 Band of Cyanuric Fluoride,"Patrick E. Fleming and C. Weldon Mathews, J. Mol. Spectrosc.,152, 317-327 (1992).

  "A Reexamination of the A1-X1+Transition of AlBr," J. Mol. Spectrosc., 175, 31-36 (1996).