Question: What becomes of the atom if the energy of the photon is absorbed?
About the article "Photoelectric effect", section "Emission mechanism".

Candidate passages:
The photons of a light beam have a characteristic energy proportional to the frequency of the light.
In the photoemission process, if an electron within some material absorbs the energy of one photon and acquires more energy than the work function (the electron binding energy) of the material, it is ejected.
If the photon energy is too low, the electron is unable to escape the material.
Since an increase in the intensity of low-frequency light will only increase the number of low-energy photons sent over a given interval of time, this change in intensity will not create any single photon with enough energy to dislodge an electron.
Thus, the energy of the emitted electrons does not depend on the intensity of the incoming light, but only on the energy (equivalently frequency) of the individual photons.
It is an interaction between the incident photon and the outermost electrons.
Electrons can absorb energy from photons when irradiated, but they usually follow an "all or nothing" principle.
All of the energy from one photon must be absorbed and used to liberate one electron from atomic binding, or else the energy is re-emitted.
If the photon energy is absorbed, some of the energy liberates the electron from the atom, and the rest contributes to the electron's kinetic energy as a free particle.
An absorption edge, absorption discontinuity or absorption limit is a sharp discontinuity in the absorption spectrum of a substance.
These discontinuities occur at wavelengths where the energy of an absorbed photon corresponds to an electronic transition or ionization potential.
When the quantum energy of the incident radiation becomes smaller than the work required to eject an electron from one or other quantum states in the constituent absorbing atom the incident radiation ceases to be absorbed by that state.
For example, incident radiation on an atom of a wavelength that has a corresponding energy just below the binding energy of the K shell electron in that atom cannot eject the K shell electron. 
X-rays are electromagnetic waves with a wavelength less than about 10−9 m (greater than 3x1017 Hz and 1,240 eV).
A smaller wavelength corresponds to a higher energy according to the equation E=hc/λ.
("E" is Energy; "h" is Planck's constant; "c" is the speed of light; "λ" is wavelength.)
When an X-ray photon collides with an atom, the atom may absorb the energy of the photon and boost an electron to a higher orbital level or if the photon is very energetic, it may knock an electron from the atom altogether, causing the atom to ionize.
Generally, larger atoms are more likely to absorb an X-ray photon since they have greater energy differences between orbital electrons.
Soft tissue in the human body is composed of smaller atoms than the calcium atoms that make up bone, hence there is a contrast in the absorption of X-rays.
X-ray machines are specifically designed to take advantage of the absorption difference between bone and soft tissue, allowing physicians to examine structure in the human body.X-rays are also totally absorbed by the thickness of the earth's atmosphere, resulting in the prevention of the X-ray output of the sun, smaller in quantity than that of UV but nonetheless powerful, from reaching the surface. 
__NOTOC__Stokes shift is the difference (in wavelength or frequency units) between positions of the band maxima of the absorption and emission spectra (fluorescence and Raman being two examples) of the same electronic transition.
It is named after Irish physicist George G. Stokes.
When a system (be it a molecule or atom) absorbs a photon, it gains energy and enters an excited state.
One way for the system to relax is to emit a photon, thus losing its energy (another method would be the loss of heat energy).
When the emitted photon has less energy than the absorbed photon, this energy difference is the Stokes shift.
If the emitted photon has more energy, the energy difference is called an anti-Stokes shift; this extra energy comes from dissipation of thermal phonons in a crystal lattice, cooling the crystal in the process.
Yttrium oxysulfide doped with gadolinium oxysulfide is a common industrial anti-Stokes pigment, absorbing in the near-infrared and emitting in the visible portion of the spectrum.
Photon upconversion is another anti-Stokes process.  
Photons have a momentum given by "ħk" (where "ħ" is the reduced Planck constant and "k" the photon wavenumber), which is conserved in all atom-photon interactions.
Thus, when an atom absorbs a photon, it is given a momentum kick in the direction of the photon before absorption.
By detuning a laser beam to a frequency less than the resonant frequency (also known as red detuning), laser light is only absorbed if the light is frequency up-shifted by the Doppler effect; which occurs whenever the atom is moving towards the laser source.
This applies a friction force to the atom whenever it moves towards a laser source.
For cooling to occur along in all directions, the atom must see this friction force along all 3 cartesian axis; this is most easily achieved by illuminating the atom with 3 orthogonal laser beams, which are then reflected back along the same direction.