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Updated: Jul 12, 2026

Spatial Separation of Molecular Conformers and Clusters
Published on: January 9, 2014
The role of large conformational changes in efficient ultrafast internal conversion: deviations from the energy gap
Henk Fidder1, Matteo Rini, Erik T J Nibbering
1Department of Physical Chemistry, Uppsala University, Sweden. henk.fidder@fki.uu.se
Abstract:
Conversion of electronic excitation energy into vibrational energy was investigated for photochromic spiropyran molecules, using femtosecond UV-mid-IR pump-probe spectroscopy. We observe a weaker energy gap dependence than demanded by the "energy gap law". We demonstrate that large conformational changes accompanying the optical excitation can explain the observed time scale and energy gap dependence of ultrafast S(1) --> S(0) internal conversion processes. The possibility of dramatic deviations from standard energy gap law behavior is predicted. We conclude that controlling molecular conformations by rigid environments can have a substantial impact on photophysical and (bio)chemical processes.
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