A contribution to the theory of resonant two-photon absorption in a gas

A solution is obtained to the problem of the influence of level degeneracy and depolarizing collisions on the form of the spectrum of resonant two-photon absorption in gases. It is shown that such absorption may provide an effective method for the determination of the decay constants of multipole moments of electron shells. It is also demonstrated that the determination of the impact broadening parameters can be simplified by the use of an external magnetic field.