Optical Kerr Effect in Liquid Probed by Femtosecond X-ray Solution Scattering

초록

Optical Kerr effect (OKE) is a light-induced change of refractive index of a material and is known to originate from macroscopic alignment of molecules by the interaction with strong electromagnetic wave. Here we apply femtosecond X-ray solution scattering (fs-XSS) to a solution of dye in a molecular liquid to observe ultrafast change of X-ray scattering associated with OKE. Such ultrafast X-ray scattering response is different in its time scale and shape from the solvent-heating signal, which is typically observed in a liquid solution of dye. To confirm that the observed fs-XSS signal arises from OKE, we simulated theoretical difference scattering signal while assuming that the molecules are physically aligned by OKE. The simulated scattering signal well reproduces the experimentally measured scattering signal in reciprocal space, providing the microscopic origin of the OKE phenomenon. This study should not only help a better understanding of OKE at a molecular level but also facilitate data analysis of fs-XSS data.