  High sensitivity measurements in atomic spectroscopy were recently used in
Amelino-Camelia et. al. to constraint the form of possible modifications of the
energy-momentum dispersion relation resulting from Lorentz invariance violation
(LIV). In this letter we show that the same data can be used successfully to
set experimental bounds on deformations of the energy-momentum composition
rule. Such modifications are natural in models of deformed Lorentz symmetry
which are relevant in certain quantum gravity scenarios. We find the bound for
the deformation parameter $\kappa$ to be a few orders of magnitude below the
Planck scale and of the same magnitude as the next-to-leading order effect
found in Amelino-Camelia et. al. We briefly discuss how it would be possible to
distinguish between these two scenarios.
