DIFFRACTIVE IMAGING OF LASER-ALIGNED MOLECULES

University Of Chicago, Chicago IL

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Abstract

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Ultrafast x-ray pulses have the unique capability to probe in situ the behavior of molecules in the presence of intense laser fields that can be used to control molecular motion. Here we focus on controlling the rotational degree of freedom. A nonresonant, linearly polarized laser field will align a molecule by interaction with the molecule?s anisotropic polarizability;the most polarizable axis within the molecule will align parallel to the laser polarization axis. Since the laser polarization direction is under simple control with a waveplate, so is the direction of the molecule?s most polarizable axis with respect to the laboratory frame. It is even possible to extend simple 1D alignment to 3D through the use of elliptically polarized radiation. X-ray measurements of molecular structure in the presence of these intense, pulsed aligning fields in combination with theory are proposed to achieve a predictive understanding of light-induced structural distortion of molecules. This understanding will provide a foundation for analogous experiments planned for x-ray free electron laser facilities to investigate non-crystalline biomolecules.