  In this work we investigate the phenomena of acceleration radiation for a
two-level atom falling into the event horizon of a Kerr-Newman black hole. In
https://link.aps.org/doi/10.1103/PhysRevD.104.065006 (Phys. Rev. D 104 (2021)
065006), it has been shown that conformal quantum mechanics has a connection to
the generated Planck-like spectrum due to acceleration radiation. In this
particular aspect, the near horizon approximation played a significant role. In
https://link.aps.org/doi/10.1103/PhysRevD.106.025004 (Phys. Rev. D 106 (2022)
025004), we have used the beyond near horizon approximation to show that the
excitation probability attains a Planck-like spectrum irrespective of the
non-existence of an underlying conformal symmetry for a general class of static
spherically symmetric black holes. In our analysis we have gone beyond the near
horizon approximation for the rotating and charged case and even without the
consideration of the conformal symmetry we observe a similar Planck-like
spectrum. However, the coefficient of the spectrum is significantly different
from the near horizon case. We have then considered a different scenario where
a two-level atom emits multiple photons while freely falling into the event
horizon of the Kerr-Newman black hole. It is observed that the Planck factor in
the excitation probability is significantly small than that of the case of
single-photon emission (for large number of simultaneously emitted photons from
the two-level atom). Finally, we have computed the von-Neumann entropy which is
also known as the horizon brightened acceleration radiation entropy or the HBAR
entropy. We have carried out our analysis for a scalar field only to see the
effect of the charge and rotation of the black hole in this particular
scenario.
