Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Detection of light emission produced in the process of positronium
  formation   The excess energy emitted during the positronium (Ps) formation in condensed
matter may be released as light. Spectroscopic analysis of this light can be a
new method of studying the electronic properties of materials. We report the
first experimental attempt, according to our knowledge, to verify the existence
of this emission process. As a result, the possibility of the emission of
photons during Ps formation is within the experimental uncertainty in two
different solids: an n-alkane and porous silica. However, it seems that the Ps
formation on the alkane surface is not accompanied by the emission of photons
with energy in the detection range of 1.6 - 3.9 eV. Various processes that can
influence the energy of the photon emitted during the Ps formation are
discussed to elucidate this issue. To aid future experiments, equations were
developed to estimate the expected ratio of light emission events to
annihilation events with the presence or absence of a photon during the Ps
formation.

36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
9
The categories of this paper are: nlin
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph
6
The categories of this paper are: astro-ph