Time Resolved Hard X-ray/Optical Transient Grating Spectroscopy on a Liquid Jet

Optical spectroscopy typically involves transitions of valence electrons within a molecular system, while X-ray spectroscopy is concerned with transitions of core electrons providing element-specific information. Combinations of both interactions are interesting in the context of nonlinear X-ray/optical wave-mixing experiments, which have been successfully demonstrated at free electron lasers (FELs) [1]–[4]. We will report some early results from an experimental study at the SwissFEL free electron laser, where we applied the novel method of hard X-ray/optical transient grating spectroscopy (XO-TG) [4] for investigation of a chemical compound solvated in water [5]. In XO-TG, typically an interfering X-ray field forms the ‘grating’, which causes a subsequent modulation of the refractive index in the sample with respect to the optical probe. In our case the X-ray induced transient grating structure at the liquid jet sample position is generated by X-ray pulses from the free electron laser, diffracted from a diamond Talbot grating [4].