All-XUV pump-probe transient absorption spectroscopy of the structural molecular dynamics of di-iodomethane

• Main Authors: Rebholz, M., Ding, T., Despré, V., Aufleger, L., Hartmann, M., Meyer, K., Stooß, V., Magunia, A., Wachs, D., Birk, P., Mi, Y., Borisova, G. D., Castanheira, C. D. C., Rupprecht, P., Schmid, G., Schnorr, K., Schröter, C. D., Moshammer, R., Loh, Zhi-Heng, Attar, A. R., Leone, S. R., Gaumnitz, T., Wörner, H. J., Roling, S., Butz, M., Zacharias, H., Düsterer, S., Treusch, R., Brenner, G., Vester, J., Kuleff, A. I., Ott, C., Pfeifer, T.
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2022
• Subjects: Science::Chemistry; Atomic Physics; Molecular Physics
• Online Access: https://hdl.handle.net/10356/154041
• Institution: Nanyang Technological University

In this work, we use an extreme-ultraviolet (XUV) free-electron laser (FEL) to resonantly excite the I: 4d5/2-σ∗ transition of a gas-phase di-iodomethane (CH2I2) target. This site-specific excitation generates a 4d core hole located at an iodine site, which leaves the molecule in a well-defined excited state. We subsequently measure the time-dependent absorption change of the molecule with the FEL probe spectrum centered on the same I: 4d resonance. Using ab initio calculations of absorption spectra of a transient isomerization pathway observed in earlier studies, our time-resolved measurements allow us to assign the timescales of the previously reported direct and indirect dissociation pathways. The presented method is thus sensitive to excited-state molecular geometries in a time-resolved manner, following a core-resonant site-specific trigger.