| Abstract: | Collisions between an emitter and the surrounding buffer gas particles influence the emission lines. A collision may perturb the emitter in its excited and ground states, cause direct transitions between the levels, and at the same time, change the velocity of the emitter. In this paper, we present a model which deals for the first time with all these effects when they occursimultaneously in each collision. The model assumes the emitter to be subject to random collisions by the surrounding gas particles which are taken to constitute a heat bath in thermal equilibrium. The collisions are assumed to be binary, instantaneous, and to occur with a probabiity given by the Poisson distribution. These assumptions are shown to be equivalent to the widely used impact approximation in the collision broadening theory. We discuss several special cases of the general result for the line shape obtained in the paper. |
