We present a method for measuring the diffusion coefficients for excited atoms in buffer gases that uses degenerate four-wave mixing. We show that, for low beam intensities and atomic densities, the relative angular response of the degenerate four-wave mixing signal is dependent on the excited state diffusion and decay rate only, and that it is independent of the ground state diffusion. We have experimentally measured the diffusion of potassium atoms in the
4P state in xenon and found that the diffusion coefficient
D at 155 \ifmmode^\circ\else\textdegree\fi{}C and 760 torr is 0.084(4) c
m2 s−−1.
Analysis of the relative angular response of the degenerate four-wave mixing signal in alkali-metal atoms mixed with a buffer gas allows direct determination of the excited-state diffusion coefficients. The measured diffusion coefficients D at 96 \ifmmode^\circ\else\textdegree\fi{}C and 760 torr for the cesium 6
P1/2 and 6
P3/2 state atoms in neon gas are 0.348(4)
cm2 ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ and 0.281(8)
cm2 ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$, respectively. \textcopyright{} 1996 The American Physical Society.
Direct Measurement of the Cesium 6P
3/2 Excited State Diffusion Coefficient in Helium Using Degenerate Four-Wave Mixing Techniques