AN ESTIMATE OF THE ABSORPTION MEAN FREE PATH FOR A PHOTON IN A GAS
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
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A photon which is emitted by an excited atom is considered, the atom being surrounded by like atoms in the ground state. In the present paper an estimate is made of how far the photon can travel before it is absorbed by a ground state atom. The selection rules of the atom are used and the Doppler shift in energy and angular momentum of the photon is taken into account. A discussion is presented which indicates how the mean free path gives an indication of whether or not the gas is optically thick. On the basis of the formula which is derived for the mean free path, it is shown that in general gases are more transparent to the shorter wavelengths than the longer ones.
- Physical Chemistry