Collisional mJ mixing and multipole relaxation in 4P2 potassium atoms

Abstract

${m}_{J}$ mixing in $4^{2}P_{\frac{1}{2}}$ and $4^{2}P_{\frac{3}{2}}$ potassium atoms as well as atomic multipole relaxation induced in K-K and K-Ar collisions were investigated by methods of atomic fluorescence spectroscopy. K vapor, pure or mixed with Ar, was placed in a kG magnetic field and irradiated with a single Zeeman component of 7665- or 7699-\AA{} resonance radiation, causing the selective excitation of the $^{2}P_{\frac{1}{2},\ensuremath{-}\frac{1}{2}}$ or $^{2}P_{\frac{3}{2},\ensuremath{-}\frac{3}{2}}$ substate. Collisions of the excited atoms with ground-state K or Ar atoms caused ${m}_{J}$ mixing which was monitored by analysis of the resulting fluorescent spectrum with a scanning Fabry-Perot interferometer. Intensity measurements on the fluorescent Zeeman components in relation to ground-state atomic densities yielded the following multipole relaxation cross sections ${\ensuremath{\Lambda}}_{J}^{(L)}$: K-K (${10}^{\ensuremath{-}12}$ ${\mathrm{cm}}^{2}$): ${\ensuremath{\Lambda}}_{\frac{1}{2}}^{(1)}=5.7\ifmmode\pm\else\textpm\fi{}0.9$, ${\ensuremath{\Lambda}}_{\frac{3}{2}}^{(1)}=8.1\ifmmode\pm\else\textpm\fi{}1.4$, ${\ensuremath{\Lambda}}_{\frac{3}{2}}^{(2)}=11.4\ifmmode\pm\else\textpm\fi{}2.0$, ${\ensuremath{\Lambda}}_{\frac{3}{2}}^{(3)}=9.8\ifmmode\pm\else\textpm\fi{}1.5$; K-Ar (${10}^{\ensuremath{-}16}$ ${\mathrm{cm}}^{2}$): ${\ensuremath{\Lambda}}_{\frac{1}{2}}^{(1)}=65\ifmmode\pm\else\textpm\fi{}10$, ${\ensuremath{\Lambda}}_{\frac{3}{2}}^{(1)}=175\ifmmode\pm\else\textpm\fi{}25$, ${\ensuremath{\Lambda}}_{\frac{3}{2}}^{(2)}=230\ifmmode\pm\else\textpm\fi{}35$, ${\ensuremath{\Lambda}}_{\frac{3}{2}}^{(3)}=190\ifmmode\pm\else\textpm\fi{}30$. The ${Q}_{J}(m\ensuremath{\leftrightarrow}{m}^{\ensuremath{'}})$ cross sections for ${m}_{J}$ mixing were derived from the ${\ensuremath{\Lambda}}_{J}^{(L)}$ as well as the cross sections for multipole decay ${\ensuremath{\sigma}}_{J}^{(L)}={\ensuremath{\Lambda}}_{J}^{(L)}+{\ensuremath{\sigma}}_{J}^{(0)}$. The experimental results are in good agreement with theoretical calculations.