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Seeing with the nano-eye: imaging structure, coupling, and dynamics on the molecular scale

Event Details

Event Dates: 

Friday, January 26, 2018 - 4:00pm

Seminar Location: 

  • JILA Auditorium

Speaker Name(s): 

Marcus Raschke

Speaker Affiliation(s): 

University of Colorado
Seminar Type/Subject

Scientific Seminar Type: 

  • Phys Chem/Chem Phys Seminar

Event Details & Abstract: 

Intra- and intermolecular coupling and dynamics determines chemicalreaction, charge transfer, and catalytic activity of molecules. Vibrational IRand Raman spectroscopy can provide information about structure, coupling, anddynamics underlying the properties of the molecular systems. I will discuss thecombination of plasmonic and optical antenna based scanning probe concepts withbroadband, ultrafast, and shaped laser pulses for few-nanometer spatiallyresolved vibrational spectroscopy. Probing selected vibrational markerresonances, I will present examples how to access nanoscale chemicalcomposition, domain morphologies, or disorder down to the single moleculelimit. Specifically, I will introduce a new form of optical crystallographytaking advantage of the anisotropy of the vibrational molecular responseselectively probed by tip-scattering for imaging crystalline phases andorientation. We further directly measure molecular coupling through frequencyshifts of a vibrational marker in heterogeneous environments and associatedinhomogeneities in vibrational dephasing. In combination with ultrafastspectroscopy, the vibrational coherent evolution of homogeneous sub-ensemblescoupled to their bath can be observed. The experiments reveal details of themolecular dynamics over a wide range from 10’s fs intramolecular dephasing toseconds for low temperature structural reorientations. Our approach thusprovides real-space and real-time visualization of molecular dynamics thatdefine the properties of many functional materials.

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