  In a recent experiment, Hirjibehedin {\it et al.} [Science {\bf 317}, 1199
(2007)] performed inelastic tunneling spectroscopy of a single iron atom
absorbed on a nonmagnetic substrate. The observed steps in the differential
conductance marked the spin excitation energies. In this Letter, we explain
observed nonmonotonicities in the differential conductance by a nonequilibrium
population of the atom spin states. Furthermore, we predict super-Poissonian
current noise due to this nonequilibrium situation. By introducing an
anisotropic relaxation channel we are also able to explain the remarkable
absence of nonequilibrium features at certain conductance steps.
