Effect of μ4-O Sites on the Ultrafast Dynamics of Neutral Magnetic Copper Oxide Clusters

28 April 2025, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

The ultrafast dynamics of sub-nanometer neutral copper oxide clusters are examined with pump probe spectroscopy. Upon absorp-tion of an ultraviolet (400 nm) photon, all clusters exhibit a sub-picosecond lifetime that we attribute to carrier relaxation. We cal-culate the ground state structures and spin configurations of the neutral clusters using density functional theory to identify struc-tural features that facilitate relaxation. By comparing results across 35 clusters, ranging between Cu3O3 and Cu16O8, we find evi-dence that strong ferromagnetic coupling influences the relaxation dynamics of copper oxide clusters. The total spin magnetic mo-ments increment with addition/subtraction of each Cu atoms away from the (Cu2O)n stoichiometry and reach as high as 5 μB in the larger clusters described. The excited state lifetimes increase almost linearly by ~40 fs per additional Cu atom on the sub-ps time-scale. In each series, the formation of μ4-O atoms associated with terminal Cu atoms consistently deviate from the trendline by increasing excited state relaxation rates.

Keywords

ultrafast
femtosecond
copper oxide
cluster
magnetic moment
excited state dynamics

Supplementary materials

Title
Description
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Title
SI materials Sayres-m4-O-Dynamics:
Description
Figure S1 presents the transient dynamics and fits for the Cu-nO6 – CunO8 cluster series, Figure S2-S7 shows the UV-Vis and charge transfer properties of the excited states, and Figures S8-S9 show the transient dynamics and fits for the CunO9 – CunO13 cluster series. Table S1 presents the fitting coefficients for the experimental fits.
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