is the Doppler effect for atomic spectra a purely realistic effect?
i am now studying the Doppler effect in a thermal atomic gas If an atom travels in velocity v along x direction at some time, it emits a photon in some direction the momentum of the emitted photon can be well approximated with the free one thus the momentum of the atom after the emission is well defined We can then determine the energy of the photon with the energy conservation law In this procedure, the Doppler effect apprarently depends on the MASS of the atom However, the fomulae given in the book does not depends on the MASS but only on the velocity of the atom
