  The thermal friction force acting on an atom moving relative to a thermal
photon bath is known to be proportional to an integral over the imaginary part
of the frequency-dependent atomic (dipole) polarizability. Using a numerical
approach, we find that blackbody friction on atoms either in dilute
environments or in hot ovens is larger than previously thought by orders of
magnitude. This enhancement is due to far off-resonant driving of transitions
by low-frequency thermal radiation. At typical temperatures, the blackbody
radiation maximum lies far below the atomic transition wavelengths.
Surprisingly, due to the finite lifetime of atomic levels, which gives rise to
Lorentzian line profiles, far off-resonant excitation leads to the dominant
contribution to the blackbody friction.
