CollisionalmJmixing and multipole relaxation in4P2potassium 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-Å resonance radiation, causing the selective excitation of the ${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2},-\frac{1}{2}}^{}{}_{}{}^{}$ or ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2},-\frac{3}{2}}^{}{}_{}{}^{}$ 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 ${\Lambda }_J^{\mathrm{}\left(L\right)\mathrm{}}$: K-K (${10}^{-12\mathrm{}}$ ${\mathrm{cm}}^2$): ${\Lambda }_{\frac{1}{2}}^{\mathrm{}\left(1\right)\mathrm{}}=5.7\mathrm{}\pm 0.9$, ${\Lambda }_{\frac{3}{2}}^{\mathrm{}\left(1\right)\mathrm{}}=8.1\mathrm{}\pm 1.4$, ${\Lambda }_{\frac{3}{2}}^{\mathrm{}\left(2\right)\mathrm{}}=11.4\mathrm{}\pm 2.0$, ${\Lambda }_{\frac{3}{2}}^{\mathrm{}\left(3\right)\mathrm{}}=9.8\mathrm{}\pm 1.5$; K-Ar (${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$): ${\Lambda }_{\frac{1}{2}}^{\mathrm{}\left(1\right)\mathrm{}}=65\mathrm{}\pm 10$, ${\Lambda }_{\frac{3}{2}}^{\mathrm{}\left(1\right)\mathrm{}}=175\mathrm{}\pm 25$, ${\Lambda }_{\frac{3}{2}}^{\mathrm{}\left(2\right)\mathrm{}}=230\mathrm{}\pm 35$, ${\Lambda }_{\frac{3}{2}}^{\mathrm{}\left(3\right)\mathrm{}}=190\mathrm{}\pm 30$. The $Q_J(m\leftrightarrow m^{\prime })$ cross sections for $m_J$ mixing were derived from the ${\Lambda }_J^{\mathrm{}\left(L\right)\mathrm{}}$ as well as the cross sections for multipole decay ${\sigma }_J^{\mathrm{}\left(L\right)\mathrm{}}={\Lambda }_J^{\mathrm{}\left(L\right)\mathrm{}}+{\sigma }_J^{\mathrm{}\left(0\right)\mathrm{}}$. The experimental results are in good agreement with theoretical calculations.