Analysis of Dicke narrowing in wall-coated and buffer-gas-filled atomic storage cells

Spectral lineshape narrowing of atomic vapour emission in a bufferless, wall-coated absorption cell has been analysed using the same formalism developed to describe sub-Doppler linewidths, Dicke narrowing, in a buffered cell. Within this formalism lineshapes are generated using Monte Carlo techniques. Dramatic linewidth reductions in the bufferless cell, compared with the buffered cell, occur because of the high probability that Doppler shifts before and after a particular wall collision will cancel each other. The formalism described allows more physical insight than the classic one-dimensional box model previously invoked to explain spectra narrowing in bufferless, wall-coated cells. Additionally, this formalism reveals a correlation between post-collision velocities and intercollision times in the buffered cell resulting in modifications of the standard Dicke analysis of these cells.