Excitation and ionization in H(1s)-H(1s) collisions

Riley, Merle E.; Ritchie, A. B.

doi:10.1088/0953-4075/32/22/306

Cited by 6 publications

(7 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1 we compare our calculated spin averaged cross sections for 2s excitation in H͑1s͒-H͑1s͒, He 1 ͑1s͒-He 1 ͑1s͒, and He 1 ͑1s͒-H͑1s͒ collisions with the most recent experiments and calculations. For H-H the oneelectron calculations of Riley and Ritchie [12] are in very good agreement with the experimental data and our twoelectron results. Their underestimate at high energies is easily understood from the fact that double-atom excitation dominates above 30 keV [15], and that process cannot be directly calculated in a one-electron model.…”

supporting

confidence: 88%

“…We limit ourselves to excitation of the target, but identical conclusions can be drawn for excitation of both partners. It is interesting to note that a remarkable agreement with experiments has been obtained by one-electron models for certain such systems [11,12]. In these models the TDSE is solved for one "active" electron while the other electron is assumed "passive" and represented by an effective potential [13].…”

mentioning

confidence: 81%

“…Upper panel, H͑2s͒ excitation in H͑1s͒-H͑1s͒ collisions: solid line, spin averaged two-electron calculations ofHansen and Dubois (1998) [15] (the solid line marked with triangles shows double-atom excitation); dashed line, one-electron calculations ofRiley and Ritchie (1999) [12]; experimental data ofHill et al (1979) [23] (᭺) and ofMorgan et al (1980) [24] (᭹). Middle panel, He 1 ͑2s͒ excitation in He 1 ͑1s͒-He 1 ͑1s͒ collisions: solid line, present spin averaged two-electron calculations.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Spin Anisotropy for Excitation in Collisions between Two One-Electron Atoms

2000

View full text Add to dashboard Cite

The singlet and triplet contributions of excitation cross sections are studied theoretically for collisions between various two one-electron atoms. The spin anisotropy is shown to have a general behavior in the important impact energy range. At low energies triplet cross sections dominate completely over the singlet ones while the opposite is true when the active electron and projectile velocities are comparable. Beyond the matching velocity regime singlet and triplet contributions become identical. We propose a general dynamical interpretation based on the analysis of the time dependency of the electron probability density and probability current density.

show abstract

supporting

confidence: 88%

mentioning

confidence: 81%

mentioning

confidence: 99%

See 1 more Smart Citation

Spin Anisotropy for Excitation in Collisions between Two One-Electron Atoms

2000

View full text Add to dashboard Cite

show abstract

“…Although there have been a number of calculations and measurements of the cross-section for this process at high collision energies (see e.g. McClure 1968;Hill, Geddes & Gilbody 1979;Shingal, Bransden & Flower 1989;Riley & Burke 1999), only a few studies have looked at its behaviour at the low energies relevant for the direct collapse model. In our fiducial model, we use the rate coefficient for this reaction given in Lenzuni, Chernoff & Salpeter (1991):…”

Section: Collisional Ionization Of H By H (Reaction 10)mentioning

confidence: 99%

Simulating the formation of massive seed black holes in the early Universe – II. Impact of rate coefficient uncertainties

Glover

2015

Mon. Not. R. Astron. Soc.

View full text Add to dashboard Cite

We investigate how uncertainties in the chemical and cooling rate coefficients relevant for a metal-free gas influence our ability to determine the critical ultraviolet field strength required to suppress H 2 cooling in high-redshift atomic cooling halos. The suppression of H 2 cooling is a necessary prerequisite for the gas to undergo direct collapse and form an intermediate mass black hole. These black holes can then act as seeds for the growth of the supermassive black holes (SMBHs) observed at redshifts z ∼ 6. The viability of this model for SMBH formation depends on the critical ultraviolet field strength, J crit : if this is too large, then too few seeds will form to explain the observed number density of SMBHs. We show in this paper that there are five key chemical reactions whose rate coefficients are uncertain enough to significantly affect J crit . The most important of these is the collisional ionization of hydrogen by collisions with other hydrogen atoms, as the rate for this process is very poorly constrained at the low energies relevant for direct collapse. The total uncertainty introduced into J crit by this and the other four reactions could in the worst case approach a factor of five. We also show that the use of outdated or inappropriate values for the rates of some chemical reactions in previous studies of the direct collapse mechanism may have significantly affected the values of J crit determined by these studies.

show abstract

“…H+H collisions play an important role in research of astrophysics and fusion sciences. [1,2] Since the excited state H(2s) has a long lifetime, the collision processes involving H(2s) are often important in hydrogen plasmas. Most of experimental work has been implemented for H(1s)+ H(1s) collisions to study the excitation to H(2s) [3−5] and H(2p) [3] , the ionization, [6−9] and H − formation processes.…”

mentioning

confidence: 99%

Theoretical Investigation on Excitation, Ionization and Capture in H(1 s , 2 s ) + H(1 s , 2 s ) Collisions

Lan-Fang

Zhu

et al. 2008

Chinese Phys. Lett.

View full text Add to dashboard Cite

Cross sections of electron-loss in H(ls)+ H(ls) collisions and total collisional destruction of H(2s) in H(ls) + H(2s) collisions are calculated by four-body classical-trajectory Monte Carlo (CTMC) method and compared with previous theoretical and experimental data over the energy range of 4–100 keV. For the former a good agreement is obtained within different four-body CTMC calculations, and for the incident energy Ep > 10keV, comparison with the experimental data shows a better agreement than the results calculated by the impact parameter approximation. For the latter, our theory predicts the correct experimental behaviour, and the discrepancies between our results and experimental ones are less than 30%. Based on the successive comparison with experiments, the cross sections for excitation to H(2p), single- and double-ionization and H- formation in H(2s)+H(2s) collisions are calculated in the energy range of 4–100keV for the first time, and compared with those in H(ls)+H(ls) and H(ls)+H(2s) collisions.

show abstract

Excitation and ionization in H(1s)-H(1s) collisions

Cited by 6 publications

References 24 publications

Spin Anisotropy for Excitation in Collisions between Two One-Electron Atoms

Spin Anisotropy for Excitation in Collisions between Two One-Electron Atoms

Simulating the formation of massive seed black holes in the early Universe – II. Impact of rate coefficient uncertainties

Theoretical Investigation on Excitation, Ionization and Capture in H(1 s , 2 s ) + H(1 s , 2 s ) Collisions

Contact Info

Product

Resources

About