| 1. |
- Forrey, Robert C., et al.
(författare)
-
Nonadiabatic coupling in cold collisions of spin-polarized metastable hydrogen atoms
- 2007
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 76:5, s. 052709-
-
Tidskriftsartikel (refereegranskat)abstract
- Previous calculations of low-temperature cross sections for collisions between spin-polarized metastable hydrogen atoms are improved to include nonadiabatic radial and angular coupling at large interatomic separations. The electrostatic dipole-quadrupole interaction produces nonadiabatic radial coupling between (2s,2p) and (2p,2p) states, while the Coriolis interaction produces nonadiabatic angular coupling. Both of these long-range contributions are handled in a space-fixed atomic gauge that is particularly convenient for a spin-polarized system. The improved theoretical results are compared with an existing experiment.
|
|
| 2. |
|
|
| 3. |
- Forrey, Robert, et al.
(författare)
-
Collisions between metastable hydrogen atoms at thermal energies
- 2000
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 85:20, s. 4245-4248
-
Tidskriftsartikel (refereegranskat)abstract
- The complex interaction potentials arising in the approach of two metastable hydrogen 2s atoms are calculated and the cross sections for ionization, excitation transfer, and elastic scattering are predicted. The measured cross section for associative ionization at E = 4.1 meV equals 2×10-15 cm2. We calculate a total ionization cross section of 2×10-13 cm2, varying as E-2/3 at higher energies. Thus it appears that dissociative ionization is the major ionization channel. We find also that double excitation transfer into two excited H(2p) atoms is still more probable with the large cross section of 9×10-12 cm2 at E = 4.1 meV varying as E-1/2 at higher energies. The detection of the resulting Lyman alpha photons would provide a diagnostic test of our predictions.
|
|
| 4. |
- Gustafsson, Magnus, 1969-, et al.
(författare)
-
Semiclassical methods for calculating radiative association rate constants for different thermodynamic conditions : Application to formation of CO, CN, and SiN
- 2019
-
Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 150:22
-
Tidskriftsartikel (refereegranskat)abstract
- It is well-known that resonances can serve as a catalyst for molecule formation. Rate constants for resonance-induced molecule formation are phenomenological as they depend upon the mechanism used to populate the resonances. Standard treatments assume tunneling from the continuum is the only available population mechanism, which means long-lived quasibound states are essentially unpopulated. However, if a fast resonance population mechanism exists, the long-lived quasibound states may be populated and give rise to a substantial increase in the molecule formation rate constant. In the present work, we show that the semiclassical formula of Kramers and ter Haar [Bull. Astron. Inst. Neth. 10, 137 (1946)] may be used to compute rate constants for radiative association in the limit of local thermodynamic equilibrium. Comparisons are made with quantum mechanical and standard semiclassical treatments, and results are shown for two limits which provide upper and lower bounds for the six most important radiative association reactions leading to the formation of CO, CN, and SiN. These results may have implications for interstellar chemistry in molecular clouds, where the environmental and thermodynamic conditions often are uncertain.
|
|
| 5. |
- Jonsell, Svante, et al.
(författare)
-
Fine Structure in Cold Collisions of Spin-Polarized H(2s) Atoms
- 2004
-
Ingår i: Physica scripta. T. - 0281-1847. ; T110, s. 299-301, s. 299-301
-
Tidskriftsartikel (refereegranskat)abstract
- We have calculated cross sections and rate coefficients for elastic scattering, ionization, and double excitation transfer in collision of two hydrogen atoms in the 2s state. We find that for collision energies between 5 × 10-10 a.u. and 10-6 a.u. elastic scattering has the largest cross section. For temperatures below 0.02 K ionization is the dominant loss process, while for higher temperatures double excitation transfer dominates. Our results for the total loss rate are found to be within a factor 2 or 3 of the error bars of recent measurements.
|
|
| 6. |
|
|
| 7. |
- Zammit, Mark C., et al.
(författare)
-
Laser-driven production of the antihydrogen molecular ion
- 2019
-
Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 100:4
-
Tidskriftsartikel (refereegranskat)abstract
- The feasibility of producing the molecular antihydrogen anion (H) over bar (-)(2) in the laboratory is investigated. Utilizing reaction rates calculated here involving the interaction of laser excited-state antihydrogen atoms held in magnetic minimum traps, key processes are identified that could lead to anion production, as well as competing effects leading to anti-atom loss. These are discussed in the context of present-day and near-future experimental capabilities.
|
|
