Photon's Energy to Kinetic Energy

Melchoir asked in the "tired Light" forum:

quote:

---

What is the actual mechanism that allows the atomic nucleus to pick up and convert photons into kinetic energy?

---

How does this fit in with the mechanism used to explain light spectra, i.e., atoms can only absorb photons of a particular frequency and the rest are transmitted? Can any frequency be absorbed, but only frequencies that cause a jump in a quantum energy level are stable?If this is accurate, how do the energy jumps which don't cause a quantum jump lose some of their energy to the kinetic energy of the atom?

I am aware of Compton Scattering and Line Spectra, but for some reason I can't reconcile the two.Here is my reasoning. The theory I have learned behind spectral lines is that a atoms electrons can only absorb energy in with specific energies, i.e., specific wavelengths. The rest are transmitted and we are left with Fraunhofer lines.Compton scattering seems to imply that an atom can absorb any frequency of energy, with a part of the energy raising the electron to a higher orbital and rest being converted to kinetic energy.Or does Compton scattering only apply to free electrons, and a photon can increase the kinetic energy of the electron while reducing its own energy.Can a photon, in general, increase an atoms kinetic energy?