The total cross sections for disorientation (σ1) and disalignment (σ2) of 42P3/2 potassium atoms, induced in collisions with the ground-state atoms, have been determined using a modified Zeeman scanning method. Potassium vapor at densities of the order of 1011 cm−3, contained in a fluorescence cell located in a kilogauss variable magnetic field, was irradiated with circularly polarized 7665 Å resonance radiation emitted from a discharge lamp located in a constant field of 5.4 kG. Scans of the variable field permitted selective excitation of single Zeeman components in the absorbing vapor. The σ+ and σ− components of the resulting resonance fluorescence emitted parallel to the scanning field were monitored in relation to the vapor density, as were the π and σ components emitted in the perpendicular direction. As the vapor density increased so did the frequency of the collisions which caused transfers among the Zeeman states in the vapor and thus disorientation and disalignment. The observed dependence of circular and linear depolarization of the fluorescence on the potassium density yielded the cross sections σ1 = 17 × 10−12 cm2 and σ2 = 21 × 10−2 cm2, corrected for imprisonment of radiation.
A modified Zeeman scanning method was used to excite selectively the magnetic substates of the
42P21 potassium atoms mixed with inert gases and placed in a strong magnetic field. The resulting potassium-inert-gas atomic collisions induced
mJ mixing in potassium, which manifested itself by the depolarization of the potassium resonance fluorescence. The polarization measurements yielded the following disorientation cross sections: K-He: 46
A˚2; K-Ne: 39
A˚2; K-A: 52
A˚2; K-Kr: 80
A˚2; K-Xe: 107
A˚2.
The mj mixing cross section for disorientation of magnetically 2 oriented potassium atoms in the 4 ^2/2 state» induced by collisions with ground state helium atoms, was measured using a modified Zeeman scanning technique.The mj substates of potassium atoms, situated in a strong magnetic field, were selectively excited and the collisionally induced mixing manifested itself by the depolarization of the potassium resonance fluorescence.The depolarization measurements yielded mixing cross -14 2 -14 2 sections ranging from 0.77 x 10 cm to 1.4 x 10 cm .It is felt that this discrepancy may be due to a selection rule for transitions between the fine structure states such that £nij = 0 is preferred.
The cross sections for disorientation of 42P1/2 potassium atoms, induced in collisions with noble gas atoms, have been determined in zero magnetic field by studying the depolarization of K(7699 Å) resonance fluorescence in relation to noble gas pressures. Potassium vapor at low density, mixed with a noble gas in a fluorescence vessel, was irradiated with circularly polarized 7699 Å potassium resonance radiation and the resulting resonance fluorescence, observed in an approximately backward direction, was analyzed with respect to circular polarization. The variation of the degree of polarization with gas pressure was interpreted on the basis of a 'J randomization' model for the collisions and yielded the following disorientation cross sections which are appropriately corrected for the effect of nuclear spin: K–He, 24 ± 4 Å2; K–Ne, 21 ± 3 Å2; K–Ar, 37 ± 5 Å2; K–Kr, 51 ± 7 Å2; K–Xe, 69 ± 9 Å2. The cross sections are significantly smaller than values obtained previously in kilogauss fields.
The cross sections for the decay of circular and of linear polarization in oriented
42P23 potassium atoms, induced in collision with inert-gas atoms, were determined in a series of fluorescence experiments. A modified Zeeman scanning method was used to populate selectively the
mJ sublevels of the
2P23 potassium atoms mixed with inert gases and placed in a strong magnetic field. Measurements of depolarization of the fluorescence, in relation to gas pressures, yielded the following depolarization cross sections: ${\ensuremath{\sigma}}_{1}$ (disorientation): K-He, 86
A˚2; K-Ne, 86
A˚2; K-Ar, 164
A˚2; K-Kr, 248
A˚2; K-Xe, 251 \AA{}. ${\ensuremath{\sigma}}_{2}$ (disalignment): K-He, 127 \AA{}; K-Ne, 120
A˚2; K-Ar, 240
A˚2, K-Kr, 301
A˚2, K-Xe, 336
A˚2. The experimental values are in satisfactory agreement with the calculations of Nikitin and Ovchinnikova.
mJ mixing in
42P21 and
42P23 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
mJ 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 (${10}^{\ensuremath{-}12}$
cm2): ${\ensuremath{\Lambda}}_{\frac{1}{2}}^{(1)}=5.7\ifmmode\pm\else\textpm\fi{}0.9$, ${\ensuremath{\Lambda}}_{\frac{3}{2}}^{(1)}=8.1\ifmmode\pm\else\textpm\fi{}1.4$, ${\ensuremath{\Lambda}}_{\frac{3}{2}}^{(2)}=11.4\ifmmode\pm\else\textpm\fi{}2.0$, ${\ensuremath{\Lambda}}_{\frac{3}{2}}^{(3)}=9.8\ifmmode\pm\else\textpm\fi{}1.5$; K-Ar (${10}^{\ensuremath{-}16}$
cm2): ${\ensuremath{\Lambda}}_{\frac{1}{2}}^{(1)}=65\ifmmode\pm\else\textpm\fi{}10$, ${\ensuremath{\Lambda}}_{\frac{3}{2}}^{(1)}=175\ifmmode\pm\else\textpm\fi{}25$, ${\ensuremath{\Lambda}}_{\frac{3}{2}}^{(2)}=230\ifmmode\pm\else\textpm\fi{}35$, ${\ensuremath{\Lambda}}_{\frac{3}{2}}^{(3)}=190\ifmmode\pm\else\textpm\fi{}30$. The ${Q}_{J}(m\ensuremath{\leftrightarrow}{m}^{\ensuremath{'}})$ cross sections for
mJ 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.