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1.
Phys Chem Chem Phys ; 17(29): 19491-9, 2015 Jul 15.
Article in English | MEDLINE | ID: mdl-26146364

ABSTRACT

Energy relaxation between two electronic states of a molecule is mediated by a set of relevant vibrational states. We describe this fundamental process in a fully quantum mechanical framework based on first principles. This approach explains population transfer rates as well as describes the entire transient absorption signal as vibronic transitions between electronic states. By applying this vibronic energy relaxation approach to carotenoids, we show that ß-carotene's transient absorption signal can be understood without invoking the intensely debated S* electronic state. For a carotenoid with longer chain length, we find that vibronic energy relaxation does not suffice to explain all features in the transient absorption spectra, which we relate to an increased ground state structural inhomogeneity. Our modeling approach is generally applicable to photophysical deactivation processes in molecules. As such, it represents a well-founded alternative to data fitting techniques such as global target analysis.


Subject(s)
Carotenoids/chemistry , Quantum Theory , Algorithms , Molecular Structure , Vibration , beta Carotene/chemistry
2.
Opt Express ; 18(26): 27846-57, 2010 Dec 20.
Article in English | MEDLINE | ID: mdl-21197058

ABSTRACT

We show that weakly guiding nonlinear waveguides support stable propagation of rotating spatial solitons (azimuthons). We investigate the role of waveguide symmetry on the soliton rotation. We find that azimuthons in circular waveguides always rotate rigidly during propagation and the analytically predicted rotation frequency is in excellent agreement with numerical simulations. On the other hand, azimuthons in square waveguides may experience spatial deformation during propagation. Moreover, we show that there is a critical value for the modulation depth of azimuthons above which solitons just wobble back and forth, and below which they rotate continuously. We explain these dynamics using the concept of energy difference between different orientations of the azimuthon.


Subject(s)
Models, Theoretical , Refractometry/instrumentation , Refractometry/methods , Computer Simulation , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Light , Mesons , Nonlinear Dynamics , Scattering, Radiation
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