Physical Review A

Spin Polarization in Proton-Krypton Charge-Exchange Collisions

Robin Shakeshaft, J. H. Macek

Published May 1, 1973• 8 citations

Abstract

In proton-krypton charge-transfer collisions hydrogen is produced in the ground state and the krypton ions are preferentially populated in the ground ($^{2}P_{\frac{3}{2}}$) state when the protons are incident at about 100 eV. The preferential population of ${\mathrm{Kr}}^{+}(^{2}P_{\frac{3}{2}})$ over ${\mathrm{Kr}}^{+}(^{2}P_{\frac{1}{2}})$ means that the hydrogen atoms will emerge spin polarized. We have calculated the spin-polarization fraction at 100 eV as a function of impact parameter and as a function of scattering angle, and the results are reported in this paper. A comparison of these results with the results of previous calculations of proton-xenon charge transfer indicates that the latter process is more suitable for producing spin-polarized hydrogen, at least for small scattering angles.

DOI: 10.1103/physreva.7.1554

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Physical Review A

Spin Polarization in Proton-Krypton Charge-Exchange Collisions

Robin Shakeshaft, J. H. Macek

Published May 1, 1973• 8 citations

Publisher

Abstract

In proton-krypton charge-transfer collisions hydrogen is produced in the ground state and the krypton ions are preferentially populated in the ground (

^{2}P_{\frac{3}{2}}

) state when the protons are incident at about 100 eV. The preferential population of

{\mathrm{Kr}}^{+}(^{2}P_{\frac{3}{2}})

over

{\mathrm{Kr}}^{+}(^{2}P_{\frac{1}{2}})

means that the hydrogen atoms will emerge spin polarized. We have calculated the spin-polarization fraction at 100 eV as a function of impact parameter and as a function of scattering angle, and the results are reported in this paper. A comparison of these results with the results of previous calculations of proton-xenon charge transfer indicates that the latter process is more suitable for producing spin-polarized hydrogen, at least for small scattering angles.

DOI: 10.1103/physreva.7.1554

Related papers

Spin exchange in the excitation of spin-polarized Na atoms by Ne+ -ion impact

Wolfgang Jitschin, S. Osimitsch, H Reihl +3 more

The 3s-3p excitation of spin-polarized Na atoms by ${\mathrm{Ne}}^{+}$ ions has been studied for impact energies ${E}_{\mathrm{lab}=200}$ eV to 6 keV, i.e., in the adiabatic regime. The total excitation cross section and the three Stokes polarization parameters of the fluorescence light have been measured. The linear polarization of the light shows a preferential excitation of the \ensuremath{\Vert} ${m}_{l}$ \ensuremath{\Vert}=1 magnetic substates. The circular polarization probes the spin orientation of the excited 3p state. At the highest impact energies investigated the experimental data are compatible with conservation of spin orientation during the collision. With decreasing impact energy, the spin polarization of the final 3p state becomes smaller than the spin polarization of the initial 3s state. This apparent spin depolarization is attributed to the exchange interaction between the Na valence electron and the unfilled ${\mathrm{Ne}}^{+}$ 2 ${p}^{5}$ core in the quasimolecule formed during the collision.The 3s-3p excitation of spin-polarized Na atoms by ${\mathrm{Ne}}^{+}$ ions has been studied for impact energies ${E}_{\mathrm{lab}=200}$ eV to 6 keV, i.e., in the adiabatic regime. The total excitation cross section and the three Stokes polarization parameters of the fluorescence light have been measured. The linear polarization of the light shows a preferential excitation of the \ensuremath{\Vert}${m}_{l}$\ensuremath{\Vert}=1 magnetic substates. The circular polarization probes the spin orientation of the excited 3p state. At the highest impact energies investigated the experimental data are compatible with conservation of spin orientation during the collision. With decreasing impact energy, the spin polarization of the final 3p state becomes smaller than the spin polarization of the initial 3s state. This apparent spin depolarization is attributed to the exchange interaction between the Na valence electron and the unfilled ${\mathrm{Ne}}^{+}$ 2${p}^{5}$ core in the quasimolecule formed during the collision.

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Spin exchange in hydrogen–antihydrogen collisions

Alexei Yu. Voronin, Piotr Froelich

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arXiv:0907.4444Journal of Physics B Atomic Molecular and Optical PhysicsJun 1, 20092 citations

Spin-exchange cross section for a 3He+ ion incident on a Rb atom

Yasushi Arimoto, NORIYUKI SHIMAKURA, Tamio Yamagata +2 more

Spin-exchange cross sections between a ${}^{3}{\mathrm{He}}^{+}$ ion and a Rb atom were calculated in a ${}^{3}{\mathrm{He}}^{+}$ impact-energy range from 0.01 to 10 keV/amu by the semiclassical close-coupling method based on the molecular-orbital expansion. The previous calculation in which only two states of the ${}^{3}{\mathrm{He}}^{+}$ $(1s{ }^{2}S)+\mathrm{Rb}(5s{ }^{2}S)$ system were taken into account overestimated the experimental result at 6.33 keV/amu by orders of magnitudes, whereas the present calculation, which allowed the target excitation and electron transfer, showed a rough agreement with the experimental result. In view of the application, the spin-exchange cross sections larger than ${10}^{\ensuremath{-}14} {\mathrm{cm}}^{2},$ predicted at ${}^{3}{\mathrm{He}}^{+}$ impact energies lower than 0.3 keV/amu will hopefully provide a powerful tool for producing a highly polarized ${}^{3}\mathrm{He}$ ion beam.Spin-exchange cross sections between a ${}^{3}{\mathrm{He}}^{+}$ ion and a Rb atom were calculated in a ${}^{3}{\mathrm{He}}^{+}$ impact-energy range from 0.01 to 10 keV/amu by the semiclassical close-coupling method based on the molecular-orbital expansion. The previous calculation in which only two states of the ${}^{3}{\mathrm{He}}^{+}$ $(1s{ }^{2}S)+\mathrm{Rb}(5s{ }^{2}S)$ system were taken into account overestimated the experimental result at 6.33 keV/amu by orders of magnitudes, whereas the present calculation, which allowed the target excitation and electron transfer, showed a rough agreement with the experimental result. In view of the application, the spin-exchange cross sections larger than ${10}^{\ensuremath{-}14} {\mathrm{cm}}^{2},$ predicted at ${}^{3}{\mathrm{He}}^{+}$ impact energies lower than 0.3 keV/amu will hopefully provide a powerful tool for producing a highly polarized ${}^{3}\mathrm{He}$ ion beam.

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Slow collisions of ions with Rydberg atoms

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Bulletin of the American Physical SocietyDec 1, 19920 citations

Spin Exchange in Collisions between Atoms

A. E. Glassgold

Polarization phenomena in collisions between one-electron (alkali-like) atoms are calculated with density-matrix techniques. The kinetic energies for which this treatment is valid are limited from above by the use of the Born-Oppenheimer approximation, and from below by the assumed degeneracy of the hyperfine states. The basic mechanism for polarization changes is the electron-exchange effect, as suggested by Purcell and Field and by Wittke and Dicke. The special situation of unpolarized targets is treated in some detail. In this case, there are two numbers which characterize the scattering through any angle: the absolute values of certain direct and exchange scattering amplitudes, ${F}_{d}$ and ${F}_{x}$ . All cross sections must be expressible in terms of $|{F}_{d}|$ and $|{F}_{x}|$ , and this is explicitly carried out in two cases of special interest. One refers to the case in which only the electron-spin polarization is measured, and the other to measurements of the polarization of the hyperfine states of the scattered atom. Effects of the identity of the atoms are also studied in detail.Polarization phenomena in collisions between one-electron (alkali-like) atoms are calculated with density-matrix techniques. The kinetic energies for which this treatment is valid are limited from above by the use of the Born-Oppenheimer approximation, and from below by the assumed degeneracy of the hyperfine states. The basic mechanism for polarization changes is the electron-exchange effect, as suggested by Purcell and Field and by Wittke and Dicke. The special situation of unpolarized targets is treated in some detail. In this case, there are two numbers which characterize the scattering through any angle: the absolute values of certain direct and exchange scattering amplitudes, ${F}_{d}$ and ${F}_{x}$. All cross sections must be expressible in terms of $|{F}_{d}|$ and $|{F}_{x}|$, and this is explicitly carried out in two cases of special interest. One refers to the case in which only the electron-spin polarization is measured, and the other to measurements of the polarization of the hyperfine states of the scattered atom. Effects of the identity of the atoms are also studied in detail.

Physical ReviewDec 1, 196331 citations

In proton-krypton charge-transfer collisions hydrogen is produced in the ground state and the krypton ions are preferentially populated in the ground (

^{2}P_{\frac{3}{2}}

) state when the protons are incident at about 100 eV. The preferential population of

{\mathrm{Kr}}^{+}(^{2}P_{\frac{3}{2}})

over

{\mathrm{Kr}}^{+}(^{2}P_{\frac{1}{2}})

The 3s-3p excitation of spin-polarized Na atoms by

{\mathrm{Ne}}^{+}

ions has been studied for impact energies

{E}_{\mathrm{lab}=200}

eV to 6 keV, i.e., in the adiabatic regime. The total excitation cross section and the three Stokes polarization parameters of the fluorescence light have been measured. The linear polarization of the light shows a preferential excitation of the \ensuremath{\Vert}

{m}_{l}

\ensuremath{\Vert}=1 magnetic substates. The circular polarization probes the spin orientation of the excited 3p state. At the highest impact energies investigated the experimental data are compatible with conservation of spin orientation during the collision. With decreasing impact energy, the spin polarization of the final 3p state becomes smaller than the spin polarization of the initial 3s state. This apparent spin depolarization is attributed to the exchange interaction between the Na valence electron and the unfilled

{\mathrm{Ne}}^{+}

{p}^{5}

core in the quasimolecule formed during the collision.

We consider the spin-exchange in ultracold collisions of hydrogen (

H

) and antihydrogen (

\bar{H}

) atoms. The cross sections for transitions between various hyperfine states are calculated. We show that the process of spin exchange in

\bar{H}-H

collisions is basically driven by the strong force between proton and antiproton, that spin-exchange cross-sections are proportional to the difference of singlet and triplet strong force S-wave scattering lengths, while the strong force effects are enhanced about

10^9

times due to long range atomic forces. We show that any difference in hyperfine structure of

H

and

\bar{H}

(CPT violation) manifests itself in radical change of spin-exchange cross-sections energy behavior.

Spin-exchange cross sections between a

{}^{3}{\mathrm{He}}^{+}

ion and a Rb atom were calculated in a

{}^{3}{\mathrm{He}}^{+}

impact-energy range from 0.01 to 10 keV/amu by the semiclassical close-coupling method based on the molecular-orbital expansion. The previous calculation in which only two states of the

{}^{3}{\mathrm{He}}^{+}

(1s{ }^{2}S)+\mathrm{Rb}(5s{ }^{2}S)

system were taken into account overestimated the experimental result at 6.33 keV/amu by orders of magnitudes, whereas the present calculation, which allowed the target excitation and electron transfer, showed a rough agreement with the experimental result. In view of the application, the spin-exchange cross sections larger than ${10}^{\ensuremath{-}14} {\mathrm{cm}}^{2},$ predicted at

{}^{3}{\mathrm{He}}^{+}

impact energies lower than 0.3 keV/amu will hopefully provide a powerful tool for producing a highly polarized

{}^{3}\mathrm{He}

ion beam.

{F}_{d}

and

{F}_{x}

. All cross sections must be expressible in terms of

|{F}_{d}|

and

|{F}_{x}|

, and this is explicitly carried out in two cases of special interest. One refers to the case in which only the electron-spin polarization is measured, and the other to measurements of the polarization of the hyperfine states of the scattered atom. Effects of the identity of the atoms are also studied in detail.