Inelastic-collision processes in fine-structure-changing collisions have been studied by selective stepwise excitation and observation of the resulting fluorescence. Hereby, the effect of ground-state rubidium atoms colliding with excited-state rubidium atoms was investigated. The ground-state density was changed by three orders of magnitude by performing the measurements over the temperature range of 75 to 200 \ifmmode^\circ\else\textdegree\fi{}C. The cross section for fine-structure-changing collisions [i.e., $\mathrm{Rb}({6}^{2}{D}_{\frac{5}{2}})+\mathrm{Rb}({5}^{2}{S}_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{Rb}({6}^{2}{D}_{\frac{3}{2}})+\mathrm{Rb}({5}^{2}{S}_{\frac{1}{2}})$] is ${\ensuremath{\sigma}}_{\mathrm{fs}}=(1.0\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$
cm2. The cross sections for transfer out of the fine-structure doublet [i.e., $\mathrm{Rb}({6}^{2}D)+\mathrm{Rb}({5}^{2}{S}_{\frac{1}{2}})\ensuremath{\rightarrow}\mathrm{states}\mathrm{other}\mathrm{than}\mathrm{Rb}({6}^{2}D)$] is ${\ensuremath{\sigma}}_{\mathrm{tr}}=(3.8\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$
cm2. It is demonstrated that for the intermediate excited rubidium states, both the fine-structure-changing and transfer cross sections are of the order of the geometrical cross section of the excited rubidium states.
Inelastic collisional processes in fine-structure-state mixing have been studied by selective stepwise excitation and observation of the resulting fluorescence during collisions of excited rubidium
62D25 state atoms with various noble-gas atoms. It is shown that for intermediately excited rubidium atoms the fine-structure-state mixing cross sections are generally increasing from helium to xexon. The cross sections for the process $\mathrm{Rb}(6^{2}D_{\frac{5}{2}})+A(n^{1}S_{0})\ensuremath{\rightarrow}\mathrm{Rb}(6^{2}D_{\frac{3}{2}})+A(n^{1}S_{0})+\ensuremath{\Delta}E$ have the values ${\ensuremath{\sigma}}_{\mathrm{fs}}^{*}=2.4\ifmmode\pm\else\textpm\fi{}0.9, 3.1\ifmmode\pm\else\textpm\fi{}1.2, 2.6\ifmmode\pm\else\textpm\fi{}1.0, 5.8\ifmmode\pm\else\textpm\fi{}2.2, \mathrm{and} 9.3\ifmmode\pm\else\textpm\fi{}5.6$ in units of ${10}^{\ensuremath{-}14}$
cm2, where
A denotes in sequence any one of the noble gas atoms He, Ne, Ar, Kr, and Xe, respectively. Transfer cross sections for the transfer of excited Rb
62D-state atoms out of the doublet were also determined and are about an order of magnitude smaller than the fine-structure-mixing cross sections.
The thermal cross sections for inelastic transfer of excited rubidium atoms from the
n2D25 to the
n2D23 fine-structure state caused by fine-structure-changing collisions with ground-state rubidium atoms have been measured by selective stepwise excitation of the rubidium atoms and observation of the resulting fluorescence. The cross sections (in units of ${10}^{\ensuremath{-}14}$
cm2) for
n being 5-9 are 2.9\ifmmode\pm\else\textpm\fi{}0.6, 6.9\ifmmode\pm\else\textpm\fi{}1.4, 11.5\ifmmode\pm\else\textpm\fi{}2.3, 17.1\ifmmode\pm\else\textpm\fi{}3.0, and 26.0\ifmmode\pm\else\textpm\fi{}5.0, respectively. The fine-structure-changing cross sections are of the order of the geometrical cross sections and increase slightly less than
(n∗)4 for the low-lying
n2D states studied.