Direct observations of slow photo-induced structural and physical changes

Photoexcitation and the subsequent physical or chemical processes are often too rapid to capture using direct, real-time observation methods1-6. Current approaches rely mainly on time-resolved spectra derived from short-pulsed lasers with appropriate wavelengths and pulse widths for the target phenomena7-10, supplemented by some experimental techniques combined with theoretical simulations11-14. In contrast, if a material exhibits sufficiently slow changes after photoexcitation, its structures and physical properties can be directly observed and compared with theoretical and spectroscopic results. This article explores the magnetic and structural properties of a new material that displays slow relaxation from UV-excited states. The study demonstrates that both valence and inner-shell electrons are cooperatively photoexcited, transitioning to a new state influenced by spin, charge, and orbital degrees of freedom. Unlike traditional theoretical descriptions, which assume time-independent atomic orbitals as the basis for molecular orbitals, this research reveals that atomic orbitals are time-dependent during these processes. These findings offer a foundational understanding of the relaxation processes from photoexcited states and provide insights into general chemical reactions.