Cross-section measurement for the energy-transfer collisionsNa(3P)+Na(3P)→Na(5S,4D)+Na(3S)

We report our measurements of the cross sections ${\sigma }_{5S}$ and ${\sigma }_{4D}$ for the electronic-energy-transfer process $\mathrm{Na}\mathrm{}\left(3P\right)+\mathrm{Na}\mathrm{}\left(3P\right)\mathrm{}\to \mathrm{Na}\mathrm{}(5S,4D)+\mathrm{Na}\mathrm{}\left(3S\right)\mathrm{}$. To obtain these cross sections we have measured the fluorescence intensity for the transitions $5S\to 3P$, $4D\to 3P$, and $3P\to 3S$ in sodium vapor excited with a cw dye laser. The study of this electronic energy transfer is complicated and there is a large disagreement (≳${10}^4$) among reported measurements. We believe we have avoided most of the difficulties of previous experiments. Our results are ${\sigma }_{5S}=(2.0\mathrm{}\pm 0.7)\times {10}^{-15\mathrm{}}$ ${\mathrm{cm}}^2$ and ${\sigma }_{4D}=(3.2\mathrm{}\pm 1.1)\times {10}^{-15\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$, and they are compared with the results of other experiments.