Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Collision phenomena in a quantum gas

de Lph Philip Goey

Published Jan 1, 1988• 1 citation
Publisher

Abstract

The study of atomic hydrogen gas. stabilized agalnst the formation of H2 molecules by the parallel direction of the electron- and proton-spins ([formula] of [formula]). has attracted much attention in recent years" This thesis deals with the theoretical aspects of scme interesting quanturnmechanical collision phenomena appearing in such a spin-polarized gas at densitiees and ternperatures for which degeneracy effects do not playa role.

DOI
10.6100/ir276947

Related papers

Few-body collisions in a weakly interacting bose gas

Stoof, HTC (Henk)

This thesis deals with a central theme in sub-Kelvin physics: “cold” collisions and their role in experiments aiming at the achievement of Bose-Einstein condensation in spin-polarized atomic hydrogen gas. Some of the subjects studied pertain primarly to the more traditional high-density experimental scheme including its recent variants, others to low-density experiments involving magnetic traps and other advanced experimental techniques.

•Jan 1, 1989•1 citation

Cold Collision Phenomena

BOUDEWIJN J. VERHAAR, D. J. Wineland, Carl Wieman +1 more

The recent developments in laser cooling, together with a preceding decade of work on cryogenically cooled atomic hydrogen, have opened possibilities for a large variety of experiments in which collisions between very slow atoms play an important role. Examples of such experiments are reviewed with an emphasis on theoretical interpretation. We focus primarily on open problems in this field and on subjects not yet dealt with in the existing reviews. Most of the examples deal with collisions between ground state atoms. Although a future development is foreseen in the direction of longitudinally cooled and bright beams, all present examples deal with experiments on gas samples. In that connection some attention is devoted to the step required to go from a microscopic to a macroscopic description.

AIP conference proceedings•Jan 1, 1994•0 citations

A note on the spin-polarization of hydrogen atoms in a helium–hydrogen gas mixture

G. V. Klement’ev, Victor A. Kartoshkin, Sergei P. Dmitriev +1 more

In a helium–hydrogen mixture at T = 300 K, the polarization degree of hydrogen spins, both electron and nuclear, was determined to be as high as (5 ± 1)%. The role of the main processes giving rise to the formation of spin-polarized H atoms has been discussed. It is shown that an effective transfer of angular momentum from the preliminarily optically oriented He * (2 3 S 1 ) atoms to the H atoms is not due to the direct chemi-dissociation of the H 2 molecules by the He * atoms alone, or due to Penning ionization of these molecules followed by the ion-molecular rearrangement reaction H 2 + + H 2 → H 3 + + H alone, but to their summary action. The relative importance of the two mechanisms depends on the rotational temperature and total gas pressure.

Physica Scripta•Aug 1, 1996•0 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.

Physical Review•Dec 1, 1963•31 citations

The passage of positive ions through gases

H. S. W. Massey, Robert A. L. Smith

Abstract A large number of investigations have been carried out on the motion of charged particles through gases, and the subject has received added impetus from the introduction of quantum mechanics, as this theory is capable of dealing with collision phenomena in a manner that was beyond the reach of Bohr’s quantum theory. In the early days of the wave theory, many experiments were devised with a view to testing the validity of the theory; but now the foundations of quantum mechanics have been so firmly laid that we may use the theory to clarify the more complicated phenomena observed in the passage of charged particles through gases. Both from the experimental and theoretical point of view the most convenient particles to study are electrons; and, as a consequence, the phenomena observed in the collisions of electrons with gas molecules are well known and to a large extent understood. Well-marked diffraction phenomena have been observed and the relative probabilities of elastic and inelastic collisions measured for a number of gases. Although detailed theoretical explanations have not always been given, it is possible in nearly all cases to give a general description of the main processes contributing to the observed effects. For example, the Ramsauer effect is now completely explained.

Proceedings of the Royal Society of London Series A Containing Papers of a Mathematical and Physical Character•Oct 1, 1933•182 citations

Close-Coupling Calculations of Spin-Polarized Hydrogen-Deuterium Collisions

Yea-Hwang Uang, William C. Stwalley

Close-coupling calculations on the atomic collisions at cryogenic energies in a 100-kG magnetic field between spin-polarized hydrogen (H\ensuremath{\uparrow}) and deuterium (D\ensuremath{\uparrow}) have demonstrated the resonant spin-flip process postulated by Stwalley and the importance of minimizing the presence of D\ensuremath{\uparrow} in the experimental preparations of bulk H\ensuremath{\uparrow} currently in progress. Other interesting features are presented and briefly discussed including multiple Ramsauer-Townsend effects and direct electron and nuclear single- and double-spin-flip processes.

Physical Review Letters•Aug 25, 1980•12 citations
The study of atomic hydrogen gas. stabilized agalnst the formation of H2 molecules by the parallel direction of the electron- and proton-spins ([formula] of [formula]). has attracted much attention in recent years" This thesis deals with the theoretical aspects of scme interesting quanturnmechanical collision phenomena appearing in such a spin-polarized gas at densitiees and ternperatures for which degeneracy effects do not playa role.
The recent developments in laser cooling, together with a preceding decade of work on cryogenically cooled atomic hydrogen, have opened possibilities for a large variety of experiments in which collisions between very slow atoms play an important role. Examples of such experiments are reviewed with an emphasis on theoretical interpretation. We focus primarily on open problems in this field and on subjects not yet dealt with in the existing reviews. Most of the examples deal with collisions between ground state atoms. Although a future development is foreseen in the direction of longitudinally cooled and bright beams, all present examples deal with experiments on gas samples. In that connection some attention is devoted to the step required to go from a microscopic to a macroscopic description.
In a helium–hydrogen mixture at T = 300 K, the polarization degree of hydrogen spins, both electron and nuclear, was determined to be as high as (5 ± 1)%. The role of the main processes giving rise to the formation of spin-polarized H atoms has been discussed. It is shown that an effective transfer of angular momentum from the preliminarily optically oriented He * (2 3 S 1 ) atoms to the H atoms is not due to the direct chemi-dissociation of the H 2 molecules by the He * atoms alone, or due to Penning ionization of these molecules followed by the ion-molecular rearrangement reaction H 2 + + H 2 → H 3 + + H alone, but to their summary action. The relative importance of the two mechanisms depends on the rotational temperature and total gas pressure.
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, Fd{F}_{d}Fd​ and Fx{F}_{x}Fx​. All cross sections must be expressible in terms of ∣Fd∣|{F}_{d}|∣Fd​∣ and ∣Fx∣|{F}_{x}|∣Fx​∣, 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.
Abstract A large number of investigations have been carried out on the motion of charged particles through gases, and the subject has received added impetus from the introduction of quantum mechanics, as this theory is capable of dealing with collision phenomena in a manner that was beyond the reach of Bohr’s quantum theory. In the early days of the wave theory, many experiments were devised with a view to testing the validity of the theory; but now the foundations of quantum mechanics have been so firmly laid that we may use the theory to clarify the more complicated phenomena observed in the passage of charged particles through gases. Both from the experimental and theoretical point of view the most convenient particles to study are electrons; and, as a consequence, the phenomena observed in the collisions of electrons with gas molecules are well known and to a large extent understood. Well-marked diffraction phenomena have been observed and the relative probabilities of elastic and inelastic collisions measured for a number of gases. Although detailed theoretical explanations have not always been given, it is possible in nearly all cases to give a general description of the main processes contributing to the observed effects. For example, the Ramsauer effect is now completely explained.
Close-coupling calculations on the atomic collisions at cryogenic energies in a 100-kG magnetic field between spin-polarized hydrogen (H\ensuremath{\uparrow}) and deuterium (D\ensuremath{\uparrow}) have demonstrated the resonant spin-flip process postulated by Stwalley and the importance of minimizing the presence of D\ensuremath{\uparrow} in the experimental preparations of bulk H\ensuremath{\uparrow} currently in progress. Other interesting features are presented and briefly discussed including multiple Ramsauer-Townsend effects and direct electron and nuclear single- and double-spin-flip processes.