Orienting Asymmetric Molecules by Laser Fields with Twisted Polarization

主题：Orienting Asymmetric Molecules by Laser Fields with Twisted Polarization

主讲人：Ilya Sh. Averbukh

主持人：吴健  教授

时间：2017.12.5 下午3:00

地点：理科大楼A814

报告人简介：

Prof. Averbukh was educated in Moscow State University, Novosibirsk State University and Applied Physics Institute, Academy of Sciences, Kishinev, USSR before joining the Weizmann Institute of Science in 1991. Prof. Averbukhcontributed to various domains of coherent and nonlinear optics, ultrafast spectroscopy, quantum optics and applied optics. Authored and coauthored of more than hundred research papers, two books on strong field physics, and four patents. Discovered the phenomenon of fractional revivals of quantum wave packets, invented and experimentally demonstrated (together with multiple experimental collaborators throughout the world) a number of novel techniques for controlling electronic, vibrational and rotational wave packets. In particular, suggested multi-pulse approach to enhanced molecular alignment/orientation, proposed atom lithography schemes of enhanced resolution, designed and implemented a number of methods for selective laser control in molecular mixtures, suggested several techniques for controlling molecular rotation by short laser pulses, and for guiding molecular motion in electric, magnetic and optical fields. In recent years, theoretically investigated, and stimulated successful experiments on optics and kinetics of molecular super-rotors, and Anderson localization, Bloch oscillations and echo phenomena in laser-stimulated molecular rotation. Elected an APS Fellow and OSA Fellow for the research on the dynamics of quantum wave packets.

报告内容简介：

I will present results of our most recent theoretical studies on optical orientation of generic asymmetric molecules by means of the laser fields with twisted polarization. We show that such an excitation not only provides unidirectional rotation of the most polarizable molecular axis, but also induces a directed torque along this axis, which results in a transient orientation of the molecules. We reveal the mechanism behind this laser induced orientation effect, and show its classical nature. The generic asymmetric molecules are inherently chiral. Different molecular enantiomers in a mixture experience the above orienting action in opposite directions, which causes the out-of-phase oscillations of their dipole moments. The resulting microwave radiation was recently suggested to be used for the analysis/discrimination of chiral molecular mixtures. In our talk, several twisted field implementations are considered, including a pair of delayed cross-polarized laser pulses, an optical centrifuge, and polarization shaped pulses. The enantioselective orientation is demonstrated for a range of chiral molecules of various complexity, including hydrogen thioperoxide (HSOH), propylene oxide (CH₃CHCH₂O) and ethyl oxirane (CH₃CH₂CHCH₂O). The presented results demonstrate generality, versatility and robustness of this new class of optical methods for manipulating molecular enantiomers in the gas phase.