  In many extentions of standard model, dimension-5 scalar di-photon
($g_{\gamma\gamma\phi}\phi$ $F^{\mu\nu}F_{\mu\nu}$ ) or pseudoscalar di-photon
($g_{\gamma\gamma a}a\tilde{F}^{\mu\nu} F_{\mu\nu} $, ) interaction
materializes due to scale symmetry breaking or $U_A(1)$ symmetry breaking. In a
magnetized vacuum (i.e., in an external background field $\bar{F}_{\mu\nu} $)
the transverse degrees of freedom of the photons-- for such systems-- can be
described in terms of the form factors constructed out of the background field
strength tensor ($\bar{F}_{\mu\nu} $) and the same for dynamical photon
($f^{\mu\nu}$); they happen to be $\bar{F}_{\mu\nu}f^{\mu\nu}$ and
${\tilde{\bar{F}}_{\mu\nu}f^{\mu\nu}}$. These form factors transform
differently under CP transformation. While $\bar{F}_{\mu\nu}f^{\mu\nu}$
(describing polarization orthogonal to B ($|\gamma_{||} >$)) is CP even,
  the other one, ${\tilde{\bar{F}}_{\mu\nu}f^{\mu\nu}}$( describing
polarization along B ($|\gamma_\bot >$), is CP odd. In the interaction
Lagrangian, if the scalar is interchanged with the pseudoscalar, the role of
the two form factors just gets interchanged. Thus for nearly degenerate
strengths of the coupling constants ( $g_{\gamma\gamma\phi}$ and
$g_{\gamma\gamma _a}$ ) and masses ($m_\phi$ and $m_a$ ) of the respective
candidates, proper identification of one from the other may become very
difficult in laboratory or astrophysics based experiments. The basic motivation
of this investigation is to reduce this uncertainty through incorporation of
parity violating ({\it originating through magnetized medium effects }) part of
the photon self-energy in the effective Lagrangian. This step, in turn affects
the (Pseudo) Scalar Photon mixing dynamics drastically and brings out a
significant change in the spectrum of the electromagnetic beam undergoing such
interaction.
