  The optical properties of a fixed atom are well-known and investigated. For
example, the extraordinarily large cross section of a single atom as seen by a
resonant photon is essential for quantum optical applications. Mechanical
effects associated with light scattering are also well-studied, forming the
basis of laser cooling and trapping, for example. Despite this, there is one
fundamental problem that surprisingly has not been extensively studied, yet is
relevant to a number of emerging quantum optics experiments. In these
experiments, the ground state of the atom experiences a tight optical trap
formed by far-off-resonant light, to facilitate efficient interactions with
near-resonant light. However, the excited state might experience a different
potential, or even be anti-trapped. Here, we systematically analyze the effects
of unequal trapping on near-resonant atom-light interactions. In particular, we
identify regimes where such trapping can lead to significant excess heating,
and a reduction of total and elastic scattering cross sections associated with
a decreased atom-photon interaction efficiency. Understanding these effects can
be valuable for optimizing quantum optics platforms where efficient atom-light
interactions on resonance are desired, but achieving equal trapping is not
feasible.
