University of Illinois Urbana-Champaign

Extensions of the Capabilities of a Balle-Flygare Microwave Spectrometer

Emilsson, Tryggvi Ingvarsson

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Description

Title
Extensions of the Capabilities of a Balle-Flygare Microwave Spectrometer
Author(s)
Emilsson, Tryggvi Ingvarsson
Issue Date
1993
Doctoral Committee Chair(s)
Gutowsky, H.S.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • Chemistry, Analytical
  • Chemistry, Physical
Abstract
  • A series of improvements has been made on the Balle-Flygare spectrometer, covering several aspects of the operation of the instrument. Changes were made on the method for coupling signals in and out of the resonator, resulting in an improvement of signal strength ranging from a factor of 2 at high frequencies to about 100 at low frequencies. All of the electronics in the original instrument have been replaced. The sensitivity of the instrument has been improved substantially by the use of low-noise detectors and by elimination of internal sources of interference. This was achieved by using a low noise synthesizer as a source for the Local Oscillator (LO) signal, and by generating the Master Oscillator (MO) signal from the LO, with a single sideband mixer.
  • A number of nozzles are described, which permit the preparation and study of unusual molecules and weakly bonded complexes: (1) A pyrolysis nozzle was built and used to prepare dimethylsilaethylene (DMSE) and determine that the carbon-silicon double bond is 1.692 A, in good agreement with theoretical predictions. (2) Two coaxial mixing nozzles were built. The first, which operates at room temperature, allows the study of complexes containing molecules which would react, if they were premixed, e.g. the ammonia and hydrogen fluoride in H$\sb3$N-HCN-HF. The second coaxial mixing nozzle operates at high temperature and is intended for the preparation of complexes in which one component has a low vapor pressure.
  • A device was built to generate a homogeneous static electric field within the Fabry-Perot resonator, for Stark measurements. The orientation of the field can be controlled externally, allowing for convenient choice of selection rules (i.e. $\Delta$M = 0 or $\Delta$M = $\pm$1).
  • A versatile system was built for convenient and precise control over the composition of the gas samples used with the spectrometer. This system has electronic mass-flow controllers (MKS Instruments) and permits "real time" control over any arbitrary mixture of two inert carrier gases and two sample components, with an accuracy of about 1%. This system was used to probe the mechanism of formation of a number of weakly bonded complexes of the form (Ar)$\sb{\rm m}$-(HCN)$\sb{\rm n}.$
Graduation Semester
1993
Type of Resource
text
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