Physical Review A

Collisional excitation transfer in high magnetic fields. I. Theory

J. C. Gay, Werner B. Schneider

Published Sep 1, 1979• 14 citations

Abstract

The effects of strong magnetic fields on thermal collisions in a vapor are reviewed. Semiclassical and quantum-mechanical symmetry properties of the relaxation matrix are established for resonant collisions between identical atoms and nonresonant collisions with a structureless partner. The variations with field strength of the transfer rates between Zeeman sublevels for ${R}^{\ensuremath{-}3}$ dipole-dipole interaction and ${R}^{\ensuremath{-}6}$ Van der Waals interaction are obtained with an exact semiclassical computation of the collision matrix. These are then compared with those predicted with an approximate formulation by means of the symmetrical correlation function for the potential.

DOI: 10.1103/physreva.20.879

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Collisional excitation transfer in high magnetic fields. III. Potential symmetry rules and correlation function in Na(3PJ2)−Na(3S122) collisions

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Collisional excitation transfer in high magnetic fields. II. Correlation function of the interaction in H(6P13)−Hg(6S01) collisions

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Study of Hg* (63 p1)-noble gas collisions in a 200 kG field range

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Magnetic decoupling of 129Xe−Rb and 129Xe−Cs binary spin exchange

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Physical Review AFeb 28, 200323 citations

Physical Review A

Collisional excitation transfer in high magnetic fields. I. Theory

J. C. Gay, Werner B. Schneider

Published Sep 1, 1979• 14 citations

Publisher

Abstract

{R}^{\ensuremath{-}3}

dipole-dipole interaction and

{R}^{\ensuremath{-}6}

Van der Waals interaction are obtained with an exact semiclassical computation of the collision matrix. These are then compared with those predicted with an approximate formulation by means of the symmetrical correlation function for the potential.

DOI: 10.1103/physreva.20.879

Related papers

Collisional excitation transfer in high magnetic fields. III. Potential symmetry rules and correlation function in Na(3PJ2)−Na(3S122) collisions

J. C. Gay, Werner B. Schneider

An experimental study of excitation transfer between certain Zeeman sublevels of the $3^{2}P_{J}$ states in strong magnetic fields is reported for $\mathrm{Na}(3^{2}S_{\frac{1}{2}})\ensuremath{-}{\mathrm{Na}}^{*}(3^{2}P_{J})$ resonant collisions. A major decrease in the $M=\ensuremath{-}\frac{3}{2}\ensuremath{\rightarrow}M=\frac{3}{2}$ transfer rate is observed between 4 and 80 kG. Approximate calculations in the correlation-function framework are performed, and the experimental results and theoretical predictions for the field dependence are in good agreement. Some insights into the mechanisms of the collision process are deduced and the particularly important role of the electronic spin is emphasized. The importance of the symmetry properties of the interaction potential is also directly demonstrated.An experimental study of excitation transfer between certain Zeeman sublevels of the $3^{2}P_{J}$ states in strong magnetic fields is reported for $\mathrm{Na}(3^{2}S_{\frac{1}{2}})\ensuremath{-}{\mathrm{Na}}^{*}(3^{2}P_{J})$ resonant collisions. A major decrease in the $M=\ensuremath{-}\frac{3}{2}\ensuremath{\rightarrow}M=\frac{3}{2}$ transfer rate is observed between 4 and 80 kG. Approximate calculations in the correlation-function framework are performed, and the experimental results and theoretical predictions for the field dependence are in good agreement. Some insights into the mechanisms of the collision process are deduced and the particularly important role of the electronic spin is emphasized. The importance of the symmetry properties of the interaction potential is also directly demonstrated.

Physical Review ASep 1, 197910 citations

Collisional excitation transfer in high magnetic fields. II. Correlation function of the interaction in H(6P13)−Hg(6S01) collisions

J. C. Gay, Werner B. Schneider

The authors report results of the experimental study of excitation transfer between Zeeman sublevels of the $6^{3}P_{1}$ state of an even isotope of mercury in magnetic fields up to 80 kG, obtained by monitoring the transition from sudden to partially adiabatic collisions. The results are shown to be in good agreement with theoretical evaluations based on a numerical solution of the relaxation problem or on a correlation-function description using a ${R}^{\ensuremath{-}3}$ dipole-dipole interaction.The authors report results of the experimental study of excitation transfer between Zeeman sublevels of the $6^{3}P_{1}$ state of an even isotope of mercury in magnetic fields up to 80 kG, obtained by monitoring the transition from sudden to partially adiabatic collisions. The results are shown to be in good agreement with theoretical evaluations based on a numerical solution of the relaxation problem or on a correlation-function description using a ${R}^{\ensuremath{-}3}$ dipole-dipole interaction.

Physical Review ASep 1, 19799 citations

Study of Hg* (63 p1)-noble gas collisions in a 200 kG field range

J. C. Gay, A. Omont

The study of Hg* (6 3P1)-rare gas collisions in a 200 kG range of magnetic field is reported. The results show that the collisional transfer rates between the m = 0 and the m = ± 1 Zeeman sublevels of an even isotope of mercury exhibit a strikingly different dependence on the field strength according to the noble gas species. A very qualitative attempt at interpretation is given using the results of a previous theoretical model which predicts a strong anisotropy of the relaxation process when the vapour is submitted to such magnetic fields.The study of Hg* (6 3P1)-rare gas collisions in a 200 kG range of magnetic field is reported. The results show that the collisional transfer rates between the m = 0 and the m = ± 1 Zeeman sublevels of an even isotope of mercury exhibit a strikingly different dependence on the field strength according to the noble gas species. A very qualitative attempt at interpretation is given using the results of a previous theoretical model which predicts a strong anisotropy of the relaxation process when the vapour is submitted to such magnetic fields.

Journal de Physique LettresJan 1, 19768 citations

Disalignment transitions in cold collisions of 3P atoms with structureless targets in a magnetic field

Roman V. Krems, A. Dalgarno

A method for quantum-mechanical calculations of cross sections for the Zeeman transitions in collisions of ${}^{3}P$ atoms with structureless targets in a magnetic field is presented and applied to the study of magnetic and electronic relaxation in oxygen-helium and carbon-helium collisions at cold and ultracold temperatures. The rate constants for collisionally induced transitions between Zeeman levels in ground-state oxygen have large magnitudes in a 1 T field. It is shown that magnetic fields induce the forbidden ${}^{3}{P}_{1}$ $\ensuremath{\rightarrow}$ ${}^{3}{P}_{0}$ transition in ultracold collisions of carbon with helium. The cross section vanishes at zero energy for field-free collisions, but becomes infinitely large in a finite magnetic field, varying with velocity $v$ and magnetic field B as ${B}^{2}/v.$ A method for quantum-mechanical calculations of cross sections for the Zeeman transitions in collisions of ${}^{3}P$ atoms with structureless targets in a magnetic field is presented and applied to the study of magnetic and electronic relaxation in oxygen-helium and carbon-helium collisions at cold and ultracold temperatures. The rate constants for collisionally induced transitions between Zeeman levels in ground-state oxygen have large magnitudes in a 1 T field. It is shown that magnetic fields induce the forbidden ${}^{3}{P}_{1}$ $\ensuremath{\rightarrow}$ ${}^{3}{P}_{0}$ transition in ultracold collisions of carbon with helium. The cross section vanishes at zero energy for field-free collisions, but becomes infinitely large in a finite magnetic field, varying with velocity $v$ and magnetic field B as ${B}^{2}/v.$

Physical Review AJul 11, 200336 citations

Mechanism of Collisional Spin Relaxation in Σ3 Molecules

Wesley C. Campbell, Timur V. Tscherbul, Hsin-I Lu +3 more

We measure and theoretically determine the effect of molecular rotational splitting on Zeeman relaxation rates in collisions of cold 3Sigma molecules with helium atoms in a magnetic field. All four stable isotopomers of the imidogen (NH) molecule are magnetically trapped and studied in collisions with 3He and 4He. The 4He data support the predicted 1/B_{e};{2} dependence of the collision-induced Zeeman relaxation rate coefficient on the molecular rotational constant B_{e}. The measured 3He rate coefficients are much larger than the 4He coefficients, depend less strongly on B_{e}, and theoretical analysis indicates they are strongly affected by a shape resonance. The results demonstrate the influence of molecular structure on collisional energy transfer at low temperatures.We measure and theoretically determine the effect of molecular rotational splitting on Zeeman relaxation rates in collisions of cold 3Sigma molecules with helium atoms in a magnetic field. All four stable isotopomers of the imidogen (NH) molecule are magnetically trapped and studied in collisions with 3He and 4He. The 4He data support the predicted 1/B_{e};{2} dependence of the collision-induced Zeeman relaxation rate coefficient on the molecular rotational constant B_{e}. The measured 3He rate coefficients are much larger than the 4He coefficients, depend less strongly on B_{e}, and theoretical analysis indicates they are strongly affected by a shape resonance. The results demonstrate the influence of molecular structure on collisional energy transfer at low temperatures.

arXiv:0804.0265Physical Review LettersJan 6, 200953 citations

Magnetic decoupling of 129Xe−Rb and 129Xe−Cs binary spin exchange

Yuan‐Yu Jau, Nicholas N. Kuzma, W. Happer

We report calculations of the magnetic decoupling of the nuclear spin relaxation rate of ${}^{129}\mathrm{Xe}$ atoms caused by binary collisions with Rb or Cs atoms in a gas. A semiclassical approximation, using a classical path for the collision and treating the spin interactions quantum mechanically, gives results that differ by no more than 2% from calculations with the distorted-wave Born approximation. Both computational methods show that the relaxation rate decreases substantially for magnetic fields of a few tens of teslas. For ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb},$ where recent experimental measurements are available, the calculated rate coefficients at the experimental field of 9.4 T are about 80% of the calculated values at zero field. At 9.4 T, the calculated rate coefficient for ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb}$ is about one-half of the experimentally observed value. This discrepancy is probably due to inaccuracies in the van der Waals and spin-dependent potentials used in the calculations.We report calculations of the magnetic decoupling of the nuclear spin relaxation rate of ${}^{129}\mathrm{Xe}$ atoms caused by binary collisions with Rb or Cs atoms in a gas. A semiclassical approximation, using a classical path for the collision and treating the spin interactions quantum mechanically, gives results that differ by no more than 2% from calculations with the distorted-wave Born approximation. Both computational methods show that the relaxation rate decreases substantially for magnetic fields of a few tens of teslas. For ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb},$ where recent experimental measurements are available, the calculated rate coefficients at the experimental field of 9.4 T are about 80% of the calculated values at zero field. At 9.4 T, the calculated rate coefficient for ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb}$ is about one-half of the experimentally observed value. This discrepancy is probably due to inaccuracies in the van der Waals and spin-dependent potentials used in the calculations.

Physical Review AFeb 28, 200323 citations

{R}^{\ensuremath{-}3}

dipole-dipole interaction and

{R}^{\ensuremath{-}6}

An experimental study of excitation transfer between certain Zeeman sublevels of the

3^{2}P_{J}

states in strong magnetic fields is reported for $\mathrm{Na}(3^{2}S_{\frac{1}{2}})\ensuremath{-}{\mathrm{Na}}^{*}(3^{2}P_{J})$ resonant collisions. A major decrease in the $M=\ensuremath{-}\frac{3}{2}\ensuremath{\rightarrow}M=\frac{3}{2}$ transfer rate is observed between 4 and 80 kG. Approximate calculations in the correlation-function framework are performed, and the experimental results and theoretical predictions for the field dependence are in good agreement. Some insights into the mechanisms of the collision process are deduced and the particularly important role of the electronic spin is emphasized. The importance of the symmetry properties of the interaction potential is also directly demonstrated.

The authors report results of the experimental study of excitation transfer between Zeeman sublevels of the

6^{3}P_{1}

state of an even isotope of mercury in magnetic fields up to 80 kG, obtained by monitoring the transition from sudden to partially adiabatic collisions. The results are shown to be in good agreement with theoretical evaluations based on a numerical solution of the relaxation problem or on a correlation-function description using a ${R}^{\ensuremath{-}3}$ dipole-dipole interaction.

A method for quantum-mechanical calculations of cross sections for the Zeeman transitions in collisions of

{}^{3}P

atoms with structureless targets in a magnetic field is presented and applied to the study of magnetic and electronic relaxation in oxygen-helium and carbon-helium collisions at cold and ultracold temperatures. The rate constants for collisionally induced transitions between Zeeman levels in ground-state oxygen have large magnitudes in a 1 T field. It is shown that magnetic fields induce the forbidden

{}^{3}{P}_{1}

$\ensuremath{\rightarrow}$

{}^{3}{P}_{0}

transition in ultracold collisions of carbon with helium. The cross section vanishes at zero energy for field-free collisions, but becomes infinitely large in a finite magnetic field, varying with velocity

v

and magnetic field B as

{B}^{2}/v.

We report calculations of the magnetic decoupling of the nuclear spin relaxation rate of

{}^{129}\mathrm{Xe}

atoms caused by binary collisions with Rb or Cs atoms in a gas. A semiclassical approximation, using a classical path for the collision and treating the spin interactions quantum mechanically, gives results that differ by no more than 2% from calculations with the distorted-wave Born approximation. Both computational methods show that the relaxation rate decreases substantially for magnetic fields of a few tens of teslas. For ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb},$ where recent experimental measurements are available, the calculated rate coefficients at the experimental field of 9.4 T are about 80% of the calculated values at zero field. At 9.4 T, the calculated rate coefficient for ${}^{129}\mathrm{Xe}\ensuremath{-}\mathrm{Rb}$ is about one-half of the experimentally observed value. This discrepancy is probably due to inaccuracies in the van der Waals and spin-dependent potentials used in the calculations.