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Cooling, Collisions and non-Sticking of Polyatomic Molecules in a Cryogenic Buffer Gas Cell

We cool and study trans-Stilbene, Nile Red and Benzonitrile in a cryogenic (7K) cell filled with low density helium buffer gas. No molecule-helium cluster formation is observed, indicating limited atom-molecule sticking in this system. We place an upper limit of 5% on the population of clustered He-trans-Stilbene, consistent with a measured He-molecule collisional residence time of less than \(1 \mu s\). With several low energy torsional modes, trans-Stilbene is less rigid than any molecule previously buffer gas cooled into the Kelvin regime. We report cooling and gas phase visible spectroscopy of Nile Red, a much larger molecule. Our data suggest that buffer gas cooling will be feasible for a variety of small biological molecules. The same cell is also ideal for studying collisional relaxation cross sections. Measurements of Benzonitrile vibrational state decay results in determination of the vibrational relaxation cross sections of \(\sigma_{22} = 8x10^{-15} cm^2\) and \(\sigma_{21} = 6x10^{-15} cm^2\) for the 22 (v=1) and 21 (v=1) states. For the first time, we directly observe formation of cold molecular dimers in a cryogenic buffer gas cell and determine the dimer formation cross section to be \(\sim10^{-13} cm^2\). / Physics

Identiferoai:union.ndltd.org:harvard.edu/oai:dash.harvard.edu:1/13070052
Date21 October 2014
CreatorsPiskorski, Julia Hege
ContributorsDoyle, John M.
PublisherHarvard University
Source SetsHarvard University
Languageen_US
Detected LanguageEnglish
TypeThesis or Dissertation
Rightsopen

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