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Interfacing the Ab initio multiple spawning method with electronic structure methods in GAMESS: Photodecay of
Alexander Gaenko1, Albert DeFusco, Sergey A Varganov
1Ames Laboratory, ‡Department of Chemistry, Iowa State University , Ames, Iowa 50010, United States.
The Journal of Physical Chemistry. A
|October 21, 2014
Summary
Photoexcited trans-azomethane undergoes rapid nonradiative decay, with excited state lifetimes of 60-200 femtoseconds. Increased vibrational energy in the CNNC torsional mode shortens this decay time, matching experimental observations.
Area of Science:
- Computational Chemistry
- Photochemistry
- Molecular Dynamics
Background:
- Nonradiative decay is a key process in photochemistry.
- Understanding excited-state dynamics is crucial for controlling chemical reactions.
Purpose of the Study:
- To investigate the nonradiative decay of photoexcited trans-azomethane using nonadiabatic molecular dynamics.
- To explore the influence of initial vibrational excitation on excited-state lifetimes.
Main Methods:
- Utilized the ab initio multiple spawning (AIMS) program interfaced with the General Atomic and Molecular Electronic Structure System (GAMESS).
- Employed state-averaged complete active space self-consistent field (SA-CASSCF) method for electronic structure calculations.
- Calculated energies, gradients, and nonadiabatic coupling matrix elements.
Main Results:
- Simulated nonradiative decay of photoexcited trans-azomethane.
- Determined excited-state lifetimes ranging from approximately 60 to 200 femtoseconds.
- Found that increased vibrational excitation in the CNNC torsional mode shortens the excited-state lifetime.
Conclusions:
- The study successfully demonstrates the capabilities of the AIMS-GAMESS interface for nonadiabatic molecular dynamics.
- Results are consistent with experimental findings from time-resolved photoionization mass spectroscopy.
- Vibrational excitation plays a significant role in the excited-state dynamics and decay pathways of trans-azomethane.
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