[MOS] Tomorrow - Modern Optics and Spectroscopy Seminar with Kang-Kuen Ni

[Michelle Contos]

There will be a Modern Optics and Spectroscopy Seminar held tomorrow December 10th in 34-401A<http://whereis.mit.edu/?go=34> at 12pm


Kang-Kuen Ni

Harvard University

“Ultracold Chemical reactions with molecules in slow motion”

Recent tools developed for cooling atoms and molecules allow certain classes of molecules to be prepared in the micro-Kelvin temperature range. This allowed the first exploration of chemistry in the ultracold regime.  Bi-alkali molecules (e.g. KRb, NaRb, RbCs, NaK...) are especially suitable for such studies, and bi-alkali collisions and reactions were probed extensively by measuring the loss rate of reactants that were prepared in certain quantum states. In these experiments, atom loss rate serves as a proxy for the chemical reaction rate. After 10 years of work using loss rates to reveal rich information about the long-range physics that determines how the reactants approach each other, including the role of quantum statistics, we recently gained the capability of direct detection of products. In particular, we combined ionization detection and ion velocity map imaging within a potassium-rubidium (KRb) quantum gas apparatus. These new tools allowed us to directly detect all relevant species in the intriguing 4-center reaction KRb + KRb -> K2Rb2* -> K2+Rb2, including the surprising detection of the intermediate complex. We found the intermediate complex to be long-lived (of order one microsecond) which we further took advantage of to control the product formation rate by an external light source. The new capability of detecting reaction products rather than merely reactant loss opens new opportunities for reaction studies.

Refreshments will be served immediately following the seminar!


Michelle Contos
Administrative Assistant
Massachusetts Institute of Technology
Department of Chemistry
77 Massachusetts Ave, 6-333
Cambridge, MA 02139
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