Special HQOC/ITAMP Joint Quantum Sciences Seminar
Thursday, January 14, 2016
1:30 PM, Jefferson 356
Prof. Ed Narevicius, Weizmann Institute of Science
"Molecular Rotor in Cold Reactions"
The role of the internal molecular degrees of freedom, such as rotation, in low energy
reactions has been unexplored experimentally despite their significance to cold and
ultracold chemistry. Particularly important to astrochemistry is the case of the most
abundant molecule in interstellar space, hydrogen, where two spin isomers with
rotationally ground and excited levels have been detected. Here we demonstrate that
quantization of molecular rotation plays a key role in cold reaction dynamics, where
rotationally excited ortho-hydrogen reacts faster due to a stronger long-range attraction.
We observe rotational state dependent non-Arrhenius universal scaling laws in
chemi-ionization reactions of para-[cid:51A53432-AF67-4076-BF68-ED1286C6ED02] and
ortho-[cid:684FB474-BF36-4D23-82C2-5A547F3855D4] by
[cid:CB168553-35B4-4C89-B236-D5A16A0C5CD3] , spanning three orders-of-magnitude in
temperature. Different scaling laws serve as a sensitive gauge enabling us to directly
determine the exact nature of the long-range intermolecular interactions. Our results show
that the quantum state of the molecular rotor determines whether or not anisotropic
long-range interactions dominate cold collisions [1]. We will also discuss the effect of
molecular rotation on orbiting resonances that we have observed in our earlier work [2,3]
in the case of normal H2. We will demonstrate that orbiting resonance structure is highly
dependent on the rotational state of a molecule.
[1] Y. Shagam, A. Klein, W. Skomorowski, R. Yun, V. Averbukh, C. Koch and E. Narevicius,
"Molecular hydrogen interacts more strongly when rotationally excited at low
temperatures leading to faster reactions", Nature Chemistry, 7 (11) 921, (2015)
[2] A. B. Henson, S. Gersten, Y. Shagam, J. Narevicius, E. Narevicius, “Observation of
Resonances in Penning Ionization Reactions at Sub-Kelvin Temperatures in Merged Beams”
Science 338, 234–238 (2012).
[3] E. Lavert-Ofir, Y. Shagam, A. B. Henson, S. Gersten, J. Klos, P. S. Zuchowski, J.
Narevicius and E. Narevicius, “Observation of the isotope effect in sub-kelvin reactions”
Nature Chemistry 6, 332–335 (2014).
Coffee will be served
--
Clare Ploucha
Faculty Assistant to Professors Lukin & Greiner and their labs
Department of Physics
17 Oxford St., Lyman 324A
Cambridge, MA 02138
P. (617) 496-2544
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