Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Structure, Photophysics and the Order-Disorder Transition to the Beta
  Phase in Poly(9,9-(di -n,n-octyl)fluorene)   X-ray diffraction, UV-vis absorption and photoluminescence (PL) spectroscopy
have been used to study the well-known order-disorder transition (ODT) to the
beta phase in poly(9,9-(di n,n-octyl)fluorene)) (PF8) thin film samples through
combination of time-dependent and temperature-dependent measurements. The ODT
is well described by a simple Avrami picture of one-dimensional nucleation and
growth but crystallization, on cooling, proceeds only after molecular-level
conformational relaxation to the so called beta phase. Rapid thermal quenching
is employed for PF8 studies of pure alpha phase samples while extended
low-temperature annealing is used for improved beta phase formation. Low
temperature PL studies reveal sharp Franck-Condon type emission bands and, in
the beta phase, two distinguishable vibronic sub-bands with energies of
approximately 199 and 158 meV at 25 K. This improved molecular level structural
order leads to a more complete analysis of the higher-order vibronic bands. A
net Huang-Rhys coupling parameter of just under 0.7 is typically observed but
the relative contributions by the two distinguishable vibronic sub-bands
exhibit an anomalous temperature dependence. The PL studies also identify
strongly correlated behavior between the relative beta phase 0-0 PL peak
position and peak width. This relationship is modeled under the assumption that
emission represents excitons in thermodynamic equilibrium from states at the
bottom of a quasi-one-dimensional exciton band. The crystalline phase, as
observed in annealed thin-film samples, has scattering peaks which are
incompatible with a simple hexagonal packing of the PF8 chains.

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The categories of this paper are: adap-org
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The categories of this paper are: math-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: q-bio
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The categories of this paper are: eess
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The categories of this paper are: stat
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: funct-an
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The categories of this paper are: astro-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: econ