Measurement of coherent vibrational dynamics with X-ray Transient Absorption Spectroscopy simultaneously at the Carbon K- and Chlorine L2,3- edges

Andrew D Ross; Diptarka Hait; Valeriu Scutelnic; Daniel M Neumark; Martin Head-Gordon; Stephen R Leone

doi:10.1038/s42005-024-01794-4

Measurement of coherent vibrational dynamics with X-ray Transient Absorption Spectroscopy simultaneously at the Carbon K- and Chlorine L_2,3- edges

Commun Phys. 2024;7(1):304. doi: 10.1038/s42005-024-01794-4. Epub 2024 Sep 13.

Authors

Andrew D Ross^#^{1

2

3}, Diptarka Hait^#^{1

2

4}, Valeriu Scutelnic^{1

2}, Daniel M Neumark^{1

2}, Martin Head-Gordon^{1

2}, Stephen R Leone^{1

2

5}

Affiliations

¹ Department of Chemistry, University of California Berkeley, Berkeley, CA 94720 USA.
² Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA.
³ Present Address: Toptica Photonics, Inc., Pittsford, NY 14534 USA.
⁴ Present Address: Department of Chemistry and PULSE Institute, Stanford University, Stanford, CA 94305 USA.
⁵ Department of Physics, University of California Berkeley, Berkeley, CA 94720 USA.

^# Contributed equally.

Abstract

X-ray Transient Absorption Spectroscopy (XTAS) is a powerful probe for ultrafast molecular dynamics. The evolution of XTAS signal is controlled by the shapes of potential energy surfaces of the associated core-excited states, which are difficult to directly measure. Here, we study the vibrational dynamics of Raman activated CCl₄ with XTAS targeting the C 1s and Cl 2p electrons. The totally symmetric stretching mode leads to concerted elongation or contraction in bond lengths, which in turn induce an experimentally measurable red or blue shift in the X-ray absorption energies associated with inner-shell electron excitations to the valence antibonding levels. The ratios between slopes of different core-excited potential energy surfaces (CEPESs) thereby extracted agree very well with Restricted Open-Shell Kohn-Sham calculations. The other, asymmetric, modes do not measurably contribute to the XTAS signal. The results highlight the ability of XTAS to reveal coherent nuclear dynamics involving < 0.01 Å atomic displacements and also provide direct measurement of forces on CEPESs.

Keywords: Chemical physics; Electronic structure of atoms and molecules; Excited states; Quantum chemistry; X-rays.