Bismuth oxyiodide
(BiOI) is a promising material for photocatalysis
combining intriguing optical and structural properties. We show that
excitation by a femtosecond laser pulse creates coherent phonons inducing
a time-variant oscillating modulation of the optical density. We find
that the two underlying frequencies originate from lattice vibrations
along the [001] crystallographic axis, the stacking direction of oppositely
charged layers in BiOI. This is consistent with a subpicosecond charge
separation driven by a built-in dipolar field. This partially screens
the field, launching coherent phonons. Further, we determine the two
major dephasing mechanisms that lead to the loss of vibronic coherence:
(i) the anharmonic decay of an optical phonon into two acoustic phonons
and (ii) phonon-carrier scattering. Our results provide a direct demonstration
of the presence of an electric field in BiOI along the [001] axis
and show its role in efficient charge separation that is crucial for
photocatalytic applications of BiOI.
Electricity generation and demand time series often are only available on a national scale. In this contribution, we derive regionalization factors to allocate publicly available national generation and demand time series for Germany to the federalstate level. We compare two different types of regionalization approaches: Static factors are based on the regional distribution of capacities or population and GPD, whereas dynamic factors take plant-specific generation time series, regionally resolved weather patterns or compositions of different load profiles into account. We observe that dynamic regionalization factors show significant temporal variability, emphasizing the limitations of static regionalization factors for a spatio-temporally more detailed representation of power system time series.
Synthesis:The reagents Bismuth (III) nitrate pentahydrate (Bi(NO3)3 • 5 H2O), D-mannitol (C6H14O6), Polyvinylpyrrodine (PVP K-25, (C6H9NO)n), Potassium chloride, -bromide, and -iodide (KX, X = Cl, Br, I), methanol (CH3OH), and ethanol (C2H5OH) were ordered from Merck and used without further purification. BiOI nanoplatelets were synthesized in a modified approach based on the protocol reported
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