Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Laboratory photo-chemistry of pyrene clusters: an efficient way to form
  large PAHs   In this work, we study the photodissociation processes of small PAH clusters
(e.g., pyrene clusters). The experiments are carried out using a quadrupole ion
trap in combination with time-of-flight (QIT-TOF) mass spectrometry. The
results show that pyrene clusters are converted into larger PAHs under the
influence of a strong radiation field. Specifically, pyrene dimer cations
(e.g., [C$_{16}$H$_{10}$$-$C$_{16}$H$_{9}$]$^+$ or C$_{32}$H$_{19}$$^+$), will
photo-dehydrogenate and photo-isomerize to fully aromatic cations (PAHs) (e.g.,
C$_{32}$H$_{16}$$^+$) with laser irradiation. The structure of new formed PAHs
and the dissociation energy for these reaction pathways are investigated with
quantum chemical calculations. These studies provide a novel efficient
evolution routes for the formation of large PAHs in the interstellar medium
(ISM) in a bottom-up process that will counteract the top-down conversion of
large PAHs into rings and chains, and provide a reservoir of large PAHs that
can be converted into C$_{60}$ and other fullerenes and large carbon cages.

17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
4
The categories of this paper are: cond-mat
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ