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SUMMARY:The Effect of Molecular Weight on the Vibronic Structure of a Dike
 topyrrolopyrrole Polymer - Dr. Sophia C. Hayes\, University of Cyprus
DTSTART:20160415T150000Z
DTEND:20160415T160000Z
UID:TALK65730@talks.cam.ac.uk
CONTACT:Dr Stephen A. Hodge
DESCRIPTION:The vibronic structure observed in absorption spectra of conju
 gated polymers can hide important information regarding the electronic tra
 nsition and it is tightly connected to the conformation of the polymer. Vi
 bronic intensities are associated with the transition dipole moment and th
 e change in the excited state structure relative to that of the ground sta
 te. In the solid state\, vibronic intensities have been related to polymer
  aggregation and order. In this presentation\, we will address the influen
 ce of molecular weight on the vibronic structure of a diketopyrrolopyrrole
  polymer in solution using Resonance Raman Spectroscopy (RRS). The intensi
 ties of RR bands are associated with structural changes upon electronic ex
 citation and are thus directly related to the displacement between the gro
 und and excited state potential energy surface minima along specific norma
 l coordinates\, determining in turn the shape of absorption spectra. Quant
 ification of the intensities of the RR bands and analysis in combination w
 ith the absorption spectrum (a method called resonance Raman intensity ana
 lysis) can provide valuable information for the excited state potential en
 ergy surface landscape in the Frank-Condon region\, a difficult region to 
 probe with other methods.  We use this method to analyze the different vib
 ronic structure exemplified by different molecular weight fractions of a c
 onjugate polymer\, offering in addition an explanation for the high absorp
 tion exemplified by this polymer.
LOCATION:Cambridge Graphene Centre\, 9 JJ Thomson Avenue\, Cambridge CB3 O
 FA\, UK
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