The ongoing development of high-harmonic generation is supporting continuous progress in the development of new techniques for probing ultrafast chemical dynamics. In this lecture, I will highlight two recent developments which offer a complementary view of chemical dynamics. In the first part, I will discuss element-specific transient absorption spectroscopy at the L-edges of sulfur and the K-edge of carbon [1]. These measurements reveal the detailed evolution of unoccupied electronic states during sub-50-fs dissociation reactions of SF$_6^+$ and CF$_4^+$. In particular, they reveal large energy shifts of the final states, Rydberg-valence mixing, as well as the splitting of molecular shape resonances induced by photodissociation. In the second part, I will discuss XUV photoelectron spectroscopy of the non-adiabatic dynamics of NO$_2$ [2]. This technique reveals the detailed evolution of occupied electronic states by projecting the excited-state wave packet onto multiple final states of the cation. This multi-dimensional view provides a precise picture of the temporal evolution of both electronic and nuclear configurations as the excited wave packet crosses a conical intersection, performs large-amplitude motion and eventually dissociates to the photoproducts.

Probing chemical dynamics by soft-X-ray transient absorption and XUV photoelectron spectroscopy

256th National Meeting (2018)

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