Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Direct observation of free excitons in luminescence spectra of xenon
  clusters
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
36
The categories of this paper are: cmp-lg