Research in plasmonics of nano-scale metallic substances is a hot topic due to its potential applications across a broad range of fields. However, understanding the fast plasmon decay mechanisms has been a challenge both experimentally and computationally. Among the theoretical simulation methods, real-time density functional theory (RT-TDDFT) is a great tool to monitor the electron dynamics of molecules subjected to an electric field. Herein, we use the RT-TDDFT method to identify the possible plasmon decay mechanisms of a bare tetrahedral Ag<sub>8</sub> nanocluster. We excite the system with two resonant frequencies and examine changes in the dipole response. Variation of density matrix elements related to occupied and virtual orbital pairs reveals that the one-photon allowed transitions, excited due to the resonant energy, decay into high energy transitions, specifically to two-photon allowed transitions. The tetrahedral point group symmetry assignments of these transitions confirm that some of these high energy transitions are only allowed for two-photon absorption while others are permitted to be activated from both one and two photons. To this end, nanoparticles with tetrahedral shapes may be of great interest for their unique plasmonic properties. Moreover, this work suggests that the plasmonic nature of the system plays an important role in accumulating an enormous amount of energy to enhance non-linear processes.

Real-time electron dynamics of tetrahedral Ag<sub>8</sub> cluster: Implication of one- and two-photon absorption

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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Real-time electron dynamics of tetrahedral Ag8 cluster: Implication of one- and two-photon absorption

Real-time electron dynamics of tetrahedral Ag₈ cluster: Implication of one- and two-photon absorption