title: Cooling, spectroscopy and non-sticking of trans-stilbene and Nile Red.
abstract: We create and study trans-Stilbene and Nile Red in a cryogenic (7 K) cell with a 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 μs. With its very low energy torsional modes, trans-Stilbene is less rigid than any molecule previously buffer-gas-cooled into the Kelvin regime. We also 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.
authors.affiliation: Department of Physics, Harvard University, 17 Oxford St. Cambridge, MA 02143 (USA). julia@cua.harvard.edu.
authors.forename: Julia
authors.initials: J
authors.lastname: Piskorski
authors.forename: David
authors.initials: D
authors.lastname: Patterson
authors.forename: Sandra
authors.initials: S
authors.lastname: Eibenberger
authors.forename: John M
authors.initials: JM
authors.lastname: Doyle
keywords: UV/Vis spectroscopy; buffer gas cooling; dyes/pigments; low-temperature physics; van der Waals clusters