NOZZLE DESIGN FOR A FLYGARE-BALLE MICROWAVE SPECTROMETER*
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Date
1988
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Ohio State University
Abstract
We have been experimenting with nozzle design to extend the utility of the Flygare- Balle spectrometer1 In observing rotational spectra of transient species. The spectrometer traditionally uses a single, pulsed nozzle from which a premixed gas expands into the Fabry-Perot cavity. We have now tried several modifications in which gases from two different sources are mixed in the expansion region, with a much shortened, adjustable contact time. A coaxial source is useful in avoiding unwanted reactions. It consists of a fine inner tube with a continuous (cw) flow of one gas (mixture) and an outer tube generating a pulsed beam of another. Mixing $NH_{3}$ and HX gas ordinarily produces a cloud of solid NH4X particles. However, the rotational spectrum of vapor over heated solid $NH_{4}CI (450 K)$ has recently shown it to be a hydrogen bonded $NH_{3}-HCl$ diner. We have observed rotational transitions of the latter at much larger S/N using a coaxial nozzle at ambient temperature with 5*** HCl/He in the ow Inner tube and $0.3* NH_{3}/Ar$ in the pulsed outer tube. In addition, for the first time, the microwave spectrum of the hydrogen bonded, linear trimer. NH3-HCN-HF, has been observed. Preliminary results for $B_{o}$ and $D_{1}$ are $1067.09 MHz$ and-$0.4 KHz$. For it, 5* HF/He was used in the inner tube and $0.3* NH_{3\ast} HCN/Ar$ in the outer. Further extensions and applications are in progress.
Description
$^{\ast}$ Work supported by NSF and PRF. $^{1}$ T.J.Balle, E. J. Campbell, M. R. Keenan, and W. H. Flygare. J. Chem. Phys. 72, 922 (1980). $^{2}$ E. J. Goodwin, N. W. Howard, and A. C. Legon. Chem. Phys. Lett. 131, 319 (1986).
Author Institution: Noyes Chemical Laboratory, University of Illinois
Author Institution: Noyes Chemical Laboratory, University of Illinois