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Physical Review A

Determination of ground-level depolarization rates by transmission Zeeman beat spectroscopy: Application to Sm I 4f66s2F17

R. Martin. Lowe, David S. Gough, R. J. McLean, Peter Hannaford

Published Dec 1, 1987• 12 citations
Publisher

Abstract

A polarization technique based on the detection of Zeeman quantum beats in transmission is applied to the determination of multipole relaxation rates in ground or near-ground atomic levels. With an appropriate choice of polarization and geometry, beat signals are obtained whose decay directly yields the relaxation rates of orientation or alignment. The technique has been used to study collisional depolarization in the $4{f}^{6}6{s}^{2}^{7}F_{1}$ near-ground level of Sm I by rare-gas perturbers. Derived cross sections are compared with previous, widely differing determinations.

DOI
10.1103/physreva.36.5490

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Cross sections for relaxation of circular and linear polarization of $6^{2}P_{\frac{3}{2}}$ cesium atoms, induced in collisions with ground-state He, Ne, Ar, and Xe, have been determined by Zeeman scanning techniques. A fluorescence cell containing low-pressure cesium vapor together with a buffer gas was irradiated with circularly or linearly polarized 8521-\AA{} Cs resonance radiation, producing excited and polarized Cs atoms which became depolarized in subsequent collisions with the buffer-gas atoms. The resulting depolarization of the cesium resonance fluorescence was monitored in relation to buffer-gas pressure (0-10 Torr) and to the strength of the ambient magnetic field (0-10 kG). At low fields at which the nuclear spin $\stackrel{\ensuremath{\rightarrow}}{\mathrm{I}}$ is coupled to the electronic angular momentum $\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}$, the measurements yielded depolarization cross sections $Q(\mathrm{circ}.)$ and $Q(\mathrm{lin}.)$, which agree within experimental error with theoretical values calculated for spin-coupled conditions. At kilogauss fields with $\stackrel{\ensuremath{\rightarrow}}{\mathrm{I}}$ and $\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}$ decoupled, the experiments produced cross sections for disorientation and disalignment, which are also in satisfactory agreement with the appropriate theoretical predictions. The results indicate that the nuclear spin has a more pronounced effect on the collisional relaxation of the atomic dipole than of the quadrupole.

Physical Review A•Dec 1, 1976•13 citations

Collisional depolarization of Zeeman coherences in the 133 Cs 6p 2 P 3/2 level: Double-resonance two-photon polarization spectroscopy

Servet Bayram, Seda Kin, M. J. Welsh +1 more

An experimental investigation of the Cs 6s 2S1/2→6p 2P3/2→10s 2S1/2 double-resonance two-photon polar-ization spectrum has been made. In the investigation, a linear polarization degree was measured to extract the alignment depolarization cross section in the cesium 6p 2P3/2 level due to collisions between ground-level argon and excited 6p 2P3/2 cesium atoms over the Zeeman coherences. The spectra show strong depolarization of the Cs 6p 2P3/2 level. The measured alignment depolarization cross section value of 186 58 Å2 is in good agreement with the experiment and theoretical predictions. DOI: 10.1103/PhysRevA.73.042713 PACS numbers: 32.80.t, 32.70.n I.

•Jan 1, 2006•2 citations
A polarization technique based on the detection of Zeeman quantum beats in transmission is applied to the determination of multipole relaxation rates in ground or near-ground atomic levels. With an appropriate choice of polarization and geometry, beat signals are obtained whose decay directly yields the relaxation rates of orientation or alignment. The technique has been used to study collisional depolarization in the 4{f}^{6}6{s}^{2}^{7}F_{1} near-ground level of Sm I by rare-gas perturbers. Derived cross sections are compared with previous, widely differing determinations.
The method of a stimulated photon echo with specially selected linear polarizations of pumping pulses of a coherent resonant radiation is applied to a research of depolarizing collisions in molecular gas SF6 and its mixtures with buffer gases He and Xe. For the first time in one experiment the rates of a collisional decay of three lowest moments of polarization (population, orientation and alignment) are defined in an ensemble of gas particles. These rates of a relaxation are measured as functions on longitudinal velocities of resonant particles. In the frames of an experimental accuracy any noticeable dependence on velocities of particles was not detected both for orientation and alignment neither in pure resonant gas SF6 nor in mixtures. This result confirms the standard theoretical approach to depolarizing collisions. In pure SF6 decay rates of orientation and alignment have proved lesser than relaxation rate constant due to velocity changing (elastic) collisions. It means, that only the part of elastic collisions participates in destruction of multipole polarization moments of resonant levels. In comparison with our previous work the evidence is obtained that the relaxation of multipole moments seems to be j-dependent one in a medium of molecular gas SF6.
Stimulated photon echo technique with specially chosen linear polarizations of pumping pulses of exciting radiation is applied to investigation of depolarizing collisions in molecular gas SF6 and its mixtures with buffer gases He and Xe. For the first time, the collisional decay rates of population, orientation and alignment of SF6 levels are determined simultaneously. Translational velocity dependence of orientation and alignment collisional decay rates was under investigation. This velocity dependence proved to be negligible within the frames of experimental accuracy both in pure SF6 and in mixtures, which is in agreement with standard theoretical approach accepted for depolarizing collisions. Decay rates of orientation and alignment in pure SF6 have proved lower than velocity changing (elastic) collisions relaxation rate, which allows to conclude, that only some part of elastic collisions participates in destruction of multipole polarization moments of resonant levels. The evidence is obtained for j-dependence of multipole moments relaxation rates SF6.
An experimental investigation of the Cs $6s\phantom{\rule{0.2em}{0ex}}^{2}S_{1∕2}\ensuremath{\rightarrow}6p\phantom{\rule{0.2em}{0ex}}^{2}P_{3∕2}\ensuremath{\rightarrow}10s\phantom{\rule{0.2em}{0ex}}^{2}S_{1∕2}$ double-resonance two-photon polarization spectrum has been made. In the investigation, a linear polarization degree was measured to extract the alignment depolarization cross section in the cesium 6p2P3∕26p\phantom{\rule{0.2em}{0ex}}^{2}P_{3∕2}6p2P3∕2​ level due to collisions between ground-level argon and excited 6p2P3∕26p\phantom{\rule{0.2em}{0ex}}^{2}P_{3∕2}6p2P3∕2​ cesium atoms over the Zeeman coherences. The spectra show strong depolarization of the Cs 6p2P3∕26p\phantom{\rule{0.2em}{0ex}}^{2}P_{3∕2}6p2P3∕2​ level. The measured alignment depolarization cross section value of 186 (58)A˚2(58)\phantom{\rule{0.3em}{0ex}}{\mathrm{\AA{}}}^{2}(58)A˚2 is in good agreement with the experiment and theoretical predictions.
Cross sections for relaxation of circular and linear polarization of 62P326^{2}P_{\frac{3}{2}}62P23​​ cesium atoms, induced in collisions with ground-state He, Ne, Ar, and Xe, have been determined by Zeeman scanning techniques. A fluorescence cell containing low-pressure cesium vapor together with a buffer gas was irradiated with circularly or linearly polarized 8521-\AA{} Cs resonance radiation, producing excited and polarized Cs atoms which became depolarized in subsequent collisions with the buffer-gas atoms. The resulting depolarization of the cesium resonance fluorescence was monitored in relation to buffer-gas pressure (0-10 Torr) and to the strength of the ambient magnetic field (0-10 kG). At low fields at which the nuclear spin $\stackrel{\ensuremath{\rightarrow}}{\mathrm{I}}$ is coupled to the electronic angular momentum $\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}$, the measurements yielded depolarization cross sections Q(circ.)Q(\mathrm{circ}.)Q(circ.) and Q(lin.)Q(\mathrm{lin}.)Q(lin.), which agree within experimental error with theoretical values calculated for spin-coupled conditions. At kilogauss fields with $\stackrel{\ensuremath{\rightarrow}}{\mathrm{I}}$ and $\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}$ decoupled, the experiments produced cross sections for disorientation and disalignment, which are also in satisfactory agreement with the appropriate theoretical predictions. The results indicate that the nuclear spin has a more pronounced effect on the collisional relaxation of the atomic dipole than of the quadrupole.
An experimental investigation of the Cs 6s 2S1/2→6p 2P3/2→10s 2S1/2 double-resonance two-photon polar-ization spectrum has been made. In the investigation, a linear polarization degree was measured to extract the alignment depolarization cross section in the cesium 6p 2P3/2 level due to collisions between ground-level argon and excited 6p 2P3/2 cesium atoms over the Zeeman coherences. The spectra show strong depolarization of the Cs 6p 2P3/2 level. The measured alignment depolarization cross section value of 186 58 Å2 is in good agreement with the experiment and theoretical predictions. DOI: 10.1103/PhysRevA.73.042713 PACS numbers: 32.80.t, 32.70.n I.