Vibrational wavepacket dynamics in Fe carbene photosensitizer determined with femtosecond X-ray emission and scattering.

Kristjan Kunnus , Morgane Vacher (1) , Tobias Harlang , Kasper Kjær , Kristoffer Haldrup , Elisa Biasin , Tim van Driel , Mátyás Pápai , Pavel Chabera , Yizhu Liu , Hideyuki Tatsuno , Cornelia Timm , Erik Källman , Mickaël Delcey , Robert Hartsock , Marco Reinhard , Sergey Koroidov , Mads Laursen , Frederik Hansen , Peter Vester , Morten Christensen , Lise Sandberg , Zoltán Németh , Dorottya Sárosiné Szemes , Éva Bajnóczi , Roberto Alonso-Mori , James Glownia , Silke Nelson , Marcin Sikorski , Dimosthenis Sokaras , Henrik Lemke , Sophie Canton , Klaus Møller , Martin Nielsen , György Vankó , Kenneth Wärnmark , Villy Sundström , Petter Persson , Marcus Lundberg , Jens Uhlig , Kelly Gaffney

1 Uppsala Universitet [Uppsala]

The non-equilibrium dynamics of electrons and nuclei govern the function of photoactive materials. Disentangling these dynamics remains a critical goal for understanding photoactive materials. Here we investigate the photoinduced dynamics of the [Fe(bmip)2]2+ photosensitizer, where bmip = 2,6-bis(3-methyl-imidazole-1-ylidine)-pyridine, with simultaneous femtosecond-resolution Fe Kα and Kβ X-ray emission spectroscopy (XES) and X-ray solution scattering (XSS). This measurement shows temporal oscillations in the XES and XSS difference signals with the same 278 fs period oscillation. These oscillations originate from an Fe-ligand stretching vibrational wavepacket on a triplet metal-centered (3MC) excited state surface. This 3MC state is populated with a 110 fs time constant by 40% of the excited molecules while the rest relax to a 3MLCT excited state. The sensitivity of the Kα XES to molecular structure results from a 0.7% average Fe-ligand bond length shift between the 1 s and 2p core-ionized states surfaces.

Domaines: Chimie; Physique [physics]

Kristjan Kunnus, Morgane Vacher, Tobias Harlang, Kasper Kjær, Kristoffer Haldrup, et al.. Vibrational wavepacket dynamics in Fe carbene photosensitizer determined with femtosecond X-ray emission and scattering.. Nature Communications, 2020, 11 (1), pp.634. ⟨10.1038/s41467-020-14468-w⟩. ⟨hal-03018922⟩