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Internal Conversion Cascade in a Carbon Nanobelt: A Multiconfigurational Quantum Dynamical Study.

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Carbon nanobelts exhibit unique photophysical properties. Quantum dynamics simulations reveal rapid, coherent electronic decay followed by slower, decoherent relaxation, consistent with experimental observations.

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Area of Science:

  • Photophysics
  • Quantum Dynamics
  • Materials Science

Background:

  • Carbon nanobelts possess high symmetry and structural rigidity, leading to intriguing photophysical properties.
  • Understanding internal conversion dynamics is crucial for harnessing their potential in optoelectronic applications.

Purpose of the Study:

  • To characterize the internal conversion dynamics of a (6,6) armchair carbon nanobelt.
  • To elucidate the mechanisms governing electronic excitation decay in this system.

Main Methods:

  • Utilized multiconfigurational quantum dynamics simulations.
  • Employed the multi-layer multi-configuration time-dependent Hartree (ML-MCTDH) method.
  • Developed a symmetry-adapted linear vibronic coupling Hamiltonian for 26 electronic states and 210 vibrational modes.

Main Results:

  • Observed rapid coherent decay (<50 fs) transitioning to slower decoherent decay.
  • Identified electronic relaxation hindered by phonon bottlenecks, resulting in a stepwise internal conversion cascade.
  • Computed vibronic absorption spectrum shows good agreement with experimental data.

Conclusions:

  • The study provides a detailed characterization of internal conversion in carbon nanobelts.
  • The findings explain the observed photophysical behavior and validate the computational approach.
  • This work contributes to the fundamental understanding of excited-state dynamics in low-dimensional carbon materials.