Seminars Archive

X-ray even-order nonlinear techniques and Transient Grating spectroscopy to probe molecular chirality

Jérémy Rouxel
Argonne National Laboratory

Abstract
Monitoring molecular chirality with X-ray spectroscopies is challenging because the simplest signal, X-ray Circular Dichroism, is intrinsically weak. Various strategies to circumvent this issue by designing other windows of molecular chirality will be presented. First, even-order nonlinear spectroscopic techniques will be discussed. Most nonlinear spectroscopic techniques are performed using odd-order perturbative interactions in the incoming fields. The reason for this lies in the fact that even-order techniques vanish in centrosymmetric media or require higher order multipoles. Even-order techniques such as Sum-Frequency Generation have proven useful for probing interfaces but are limited otherwise. However, when the matter is chiral, even-order techniques do not vanish in the electric dipole approximation, enabling strong chiral sensitivity in the bulk. Theoretical works in the X-ray regime will be presented, and polarization pulse-shaping strategies will be discussed to map the corresponding molecular correlation functions. Second, an approach relying on X-ray Transient Grating, a four-wave-mixing technique, with cross-polarized pump pulses will be shown to be sensitive to molecular chirality.