Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fluorescence of pyrene-doped polystyrene films from room temperature
  down to 4 K for wavelength-shifting applications   In liquid argon-based particle detectors, slow wavelength shifters (WLSs)
could be used alongside the common, nanosecond scale, WLS tetraphenyl butadiene
(TPB) for background mitigation purposes. At room temperature, pyrene has a
moderate fluorescence light yield (LY) and a time constant of the order of
hundreds of nanoseconds. In this work, four pyrene-doped polystyrene films with
various purities and concentrations were characterized in terms of LY and decay
time constants in a range of temperature between 4 K and 300 K under
ultraviolet excitation. These films were found to have a LY between 35 and 50%
of that of evaporated TPB. All light yields increase when cooling down, while
the decays slow down. At room temperature, we observed that pyrene purity is
strongly correlated with emission lifetime: highest obtainable purity samples
were dominated by decays with emission time constants of $\sim$ 250-280 ns, and
lower purity samples were dominated by an $\sim$ 80 ns component. One sample
was investigated further to better understand the monomer and excimer emissions
of pyrene. The excimer-over-monomer intensity ratio decreases when the
temperature goes down, with the monomer emission dominating below $\sim$ 87 K.

28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
2
The categories of this paper are: math
13
The categories of this paper are: quant-ph
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an