  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.
