title: Direct Time-Domain Observation of Conformational Relaxation in Gas-Phase Cold Collisions.
abstract: Cooling molecules in the gas phase is important for precision spectroscopy, cold molecule physics, and physical chemistry. Measurements of conformational relaxation cross sections shed important light on potential energy surfaces and energy flow within a molecule. However, gas-phase conformational cooling has not been previously observed directly. In this work, we directly observe conformational dynamics of 1,2-propanediol in cold (6 K) collisions with atomic helium using microwave spectroscopy and buffer-gas cooling. Precise knowledge and control of the collisional environment in the buffer-gas allows us to measure the absolute collision cross-section for conformational relaxation. Several conformers of 1,2-propanediol are investigated and found to have relaxation cross-sections with He ranging from σ=4.7(3.0)×10(-18) cm(2) to σ>5×10(-16) cm(2). Our method is applicable to a broad class of molecules and could be used to provide information about the potential energy surfaces of previously uninvestigated molecules.
authors.affiliation: Department of Physics, Harvard University, Cambridge, MA, 02138, USA.|Department of Chemistry, Harvard University, Cambridge, MA, 02138, USA.
authors.forename: Garrett K
authors.initials: GK
authors.lastname: Drayna
authors.affiliation: Department of Physics, Harvard University, Cambridge, MA, 02138, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Hallas
authors.affiliation: Department of Physics, Harvard University, Cambridge, MA, 02138, USA.|Department of Chemistry, Harvard University, Cambridge, MA, 02138, USA.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Wang
authors.affiliation: Max-Planck-Institut für Struktur und Dynamik der Materie, Luruper Chaussee 149, 22761, Hamburg, Germany.|Center for Free-Electron Laser Science, Notkestrasse 85, 22607, Hamburg, Germany.
authors.forename: Sergio R
authors.initials: SR
authors.lastname: Domingos
authors.affiliation: Department of Physics, Harvard University, Cambridge, MA, 02138, USA.
authors.forename: Sandra
authors.initials: S
authors.lastname: Eibenberger
authors.affiliation: Department of Physics, Harvard University, Cambridge, MA, 02138, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Doyle
authors.affiliation: Department of Physics, Harvard University, Cambridge, MA, 02138, USA. dave@cua.harvard.edu.
authors.forename: David
authors.initials: D
authors.lastname: Patterson
keywords: analytical chemistry; rotational spectroscopy; spectroscopic methods; time-resolved spectroscopy