Plasma Chemistry
Both ions and neutral radicals are potential stepping-stones between the hydrogen-dominated chemistry of diffuse clouds and the complex organic chemistry observed in dense star-forming regions. We use plasma discharge to prepare these ions and radicals so that we can do laboratory spectroscopy on them.
In our laboratory, we have two plasma sources: a hollow cathode,
and a supersonic expansion source.
Our liquid-nitroge-cooled hollow cathode, based on the design of T. Amano [1],
is an efficient discharge source to produce positive ions,
especially protonated species.
The copper cathode is housed in a PVC cell where appropriate
precursor gases can flow continuously through.
A high voltage source is then coupled to an anode, positioned
halfway along the length of the cathode, and the resultant discharge
produces a plasma that fills the length of the cathode tube.
We intend to study important protonated ions in the ISM ion
chemistry such as the floppy H5
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The supersonic expansion source, based on the design of M. C. McCarthy [2], arcs through the starting of a supersonic molecular beam. This source is versatile in producing neutral molecules, radicals, ions and molecular complexes.
[1] T. Amano, J. Opt. Soc. Am. B, 2, 790 (1985).
[2] M. C. McCarthy et al., Astrophys. J. Suppl. 129, 611 (2000).