Opportunities and challenges for quantum dynamic imaging at the sub-Angstrom and femtosecond scales

Tuesday, March 14, 2017 - 3:00pm

Speaker:  Adi Natan, SLAC

Program Description

Among the most challenging and significant research fields currently emerging is using either photons or electrons to image and even control dynamics at the molecular scale. This field is driven by ultrafast coherent diffraction using x-ray free electron lasers, photoelectron self-diffraction, coincidence techniques, and advanced imaging and data analysis schemes.

Recent experiments of time-resolved crystal diffraction or nonperiodic imaging allow one to track both structure and dynamics in nanometer sized bioparticles, in photo-excited crystalline solids, and in nano-clusters dynamics.  However, realizing de-novo imaging of atomic motion within multiple molecular bonds in isolated molecules, with sub-angstrom and few-femtosecond resolutions has remained challenging.  Pioneering efforts correlated predicted signals with observed x-ray scattering images in photo-induced fragmentation of iodine or photoexcitation and isomerization of cyclohexadiene, however de-novo imaging could not be obtained.

I will present several recent results and discuss various promising imaging and analysis schemes that create such molecular movies without prior information of the system under study.  I will demonstrate how time-resolved femtosecond x-ray diffraction patterns from laser-excited molecular iodine vapor was used to capture electronic population transfer, coherent vibrational motion, dissociation, and rotational dephasing. I’ll also discuss results from photoelectron velocity map imaging and coincidence techniques as potential routes for table-top molecular movies. Finally, I will discuss future plans to create molecular movies using novel experimental and analysis methods, extending to the condensed phase and to systems of increased complexity. 

Opportunities and challenges for quantum dynamic imaging at the sub-Angstrom and femtosecond scales
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