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

Physical Review A

H¯−Li scattering and enhanced H¯ cooling

Prabal K. Sinha, Arnab Ghosh

Published Nov 16, 2005• 3 citations
Publisher

Abstract

The $s$-wave elastic phase shifts and cross sections for the $\overline{\mathrm{H}}\text{\ensuremath{-}}\mathrm{Li}$ system are predicted using an ab initio and nonadiabatic quantal method at very low energies. The smooth and monotonic change of the phase shifts with added eigenstates indicates that the leptonic potential for the present system has no barrier as noticed in the case of the $\overline{\mathrm{H}}\text{\ensuremath{-}}\mathrm{He}$ system, or even a hump which is present in $\overline{\mathrm{H}}\text{\ensuremath{-}}\mathrm{H}$ interaction. The very high value of the $s$-wave elastic cross section at zero or near zero energy implies that Li will be a more efficient buffer gas in cooling the antiatom to ultralow temperatures. This study may stimulate new experiments in thermalizing $\overline{\mathrm{H}}$ atom.

DOI
10.1103/physreva.72.052509

Related papers

s -wave elastic scattering of antihydrogen off atomic alkali-metal targets

Prabal K. Sinha, Arnab Ghosh

We have investigated the $s$-wave elastic scattering of antihydrogen atoms off atomic alkali-metal targets (Li, Na, K, and Rb) at thermal energies $({10}^{\ensuremath{-}16}--{10}^{\ensuremath{-}4}\phantom{\rule{0.3em}{0ex}}\mathrm{a.u.})$ using an atomic orbital expansion technique. The elastic cross sections of these systems at thermal energies are found to be very high compared to $\overline{\mathrm{H}}\text{\ensuremath{-}}\mathrm{H}$ and $\overline{\mathrm{H}}\text{\ensuremath{-}}\mathrm{He}$ systems. The theoretical models employed in this study are so chosen to consider long-range forces dynamically in the calculation. The mechanism of cooling suggests that Li may be considered to be a good candidate as a buffer gas for enhanced cooling of antihydrogen atoms to ultracold temperature.

Physical Review A•Mar 10, 2006•5 citations

S -wave Ps-Li and Ps-Na scattering

Sumana Chakraborty, Prabal K. Sinha, Arnab Ghosh

Projectile-elastic, target-elastic, and full close-coupling approximation models have been employed to investigate scattering of ortho-positronium off Li and Na atoms at low energies. Nine different basis sets for each system have been used to find the relative importance of atomic (target and projectile) states on the elastic scattering parameters and the convergence of the predicted results with added eigen- and pseudostates. The $s$-wave elastic phase shifts, scattering lengths and cross sections of both the systems are reported upto the incident energy $k=0.5\phantom{\rule{0.3em}{0ex}}\text{a.u.}$ and compared with the corresponding existing theoretical predictions. It has been found that the van der Waals and higher order long-range interactions play a crucial role in predicting $s$-wave elastic parameters for Ps--alkali-metal-atom systems at low energies.

Physical Review A•May 17, 2004•5 citations

Elastic scattering of two Li7 atoms

Robin Côté, A. Dalgarno, Michael J. Jamieson

Interaction potentials for the X $^{1}\mathrm{\ensuremath{\Sigma}}_{\mathrm{g}}^{+}$ and a $^{3}\mathrm{\ensuremath{\Sigma}}_{\mathrm{u}}^{+}$ states of ${\mathrm{Li}}_{2}$ are constructed and used in calculations of the elastic scattering of two $^{7}\mathrm{Li}$ atoms at ultralow temperatures. The extreme sensitivity of the cross sections to the details of the interaction potentials is demonstrated. The calculated elastic and spin-change cross sections are very large, of the order of ${10}^{\mathrm{\ensuremath{-}}13}$ ${\mathrm{cm}}^{2}$ at zero temperature. The predicted scattering length for the triplet state is negative with a value of -17.2${\mathit{a}}_{0}$. Pronounced shape resonances appear at energies of 4.9\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}8}$ a.u. in the singlet scattering and 5.5\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}7}$ a.u. in the triplet scattering.

Physical Review A•Jul 1, 1994•90 citations

Scattering of H¯(1s) off metastable helium atom at thermal energies

Prabal K. Sinha, Arnab Ghosh

Quantal calculations for scattering of ground-state antihydrogen by metastable $(n=2S)$ helium atoms have been performed using the nonadiabatic, atomic orbital expansion technique at thermal energies. The zero-energy elastic cross sections of the present systems are much greater than the corresponding value for the ground-state helium target. The low-energy elastic cross section for the singlet metastable helium $[\mathrm{He}(2\phantom{\rule{0.2em}{0ex}}^{1}S)]$ target is higher than the corresponding value when the target is in the metastable triplet state $[\mathrm{He}(2\phantom{\rule{0.2em}{0ex}}^{3}S)]$.

Physical Review A•Jun 12, 2006•2 citations

Interaction potentials and ultracold scattering cross sections for the Li+7–Li7 ion-atom system

Amrendra Pandey, M. Niranjan, N. Joshi +3 more

We calculate the isotope-independent ${\mathrm{Li}}^{+}$-Li potential energy curves for the electronic ground and first excited states. The scattering phase shifts and total scattering cross section for the $^{7}\mathrm{Li}^{+}\text{\ensuremath{-}}^{7}\mathrm{Li}$ collision are calculated, with an emphasis on the ultralow-energy domain down to the $s$-wave regime. The effect of physically motivated alterations on the calculated potential energy curves is used to determine the bound of accuracy of the low-energy scattering parameters for the ion-atom system. It is found that the scattering length for the $A{\phantom{\rule{0.16em}{0ex}}}^{2}{\mathrm{\ensuremath{\Sigma}}}_{u}^{+}$ state, ${a}_{u}=1325{a}_{0}$, is positive and has well-constrained bounds. For the $X{\phantom{\rule{0.16em}{0ex}}}^{2}{\mathrm{\ensuremath{\Sigma}}}_{g}^{+}$ state, the scattering length, ${a}_{g}=20\phantom{\rule{0.16em}{0ex}}465{a}_{0}$, has a large magnitude, as it is sensitive to the restrained change of the potential, due to the presence of a vibrational state in the vicinity of the dissociation limit.

arXiv:2005.09102•Physical Review A•May 11, 2020•10 citations

Collisional quenching at ultralow energies: Controlling efficiency with internal state selection

S. Bovino, Enrico Bodo, Franco Antonio Gianturco

Calculations have been carried out for the vibrational quenching of excited H(2) molecules which collide with Li(+) ions at ultralow energies. The dynamics has been treated exactly using the well-known quantum coupled-channel expansions over different initial vibrational levels. The overall interaction potential has been obtained from the calculations carried out earlier by our group using highly correlated ab initio methods. The results indicate that specific features of the scattering observables, e.g., the appearance of Ramsauer-Townsend minima in elastic channel cross sections and the marked increase of the cooling rates from specific initial states, can be linked to potential properties at vanishing energies (sign and size of scattering lengths) and to the presence of either virtual states or bound states. The suggestion is made such that by selecting the initial state preparation of the molecular partners, the ionic interactions would be amenable to controlling quenching efficiency at ultralow energies.

arXiv:0710.4892•The Journal of Chemical Physics•Dec 11, 2007•4 citations
The sss-wave elastic phase shifts and cross sections for the H‾\ensuremath-Li\overline{\mathrm{H}}\text{\ensuremath{-}}\mathrm{Li}H\ensuremath-Li system are predicted using an ab initio and nonadiabatic quantal method at very low energies. The smooth and monotonic change of the phase shifts with added eigenstates indicates that the leptonic potential for the present system has no barrier as noticed in the case of the H‾\ensuremath-He\overline{\mathrm{H}}\text{\ensuremath{-}}\mathrm{He}H\ensuremath-He system, or even a hump which is present in H‾\ensuremath-H\overline{\mathrm{H}}\text{\ensuremath{-}}\mathrm{H}H\ensuremath-H interaction. The very high value of the sss-wave elastic cross section at zero or near zero energy implies that Li will be a more efficient buffer gas in cooling the antiatom to ultralow temperatures. This study may stimulate new experiments in thermalizing H‾\overline{\mathrm{H}}H atom.
We have investigated the sss-wave elastic scattering of antihydrogen atoms off atomic alkali-metal targets (Li, Na, K, and Rb) at thermal energies $({10}^{\ensuremath{-}16}--{10}^{\ensuremath{-}4}\phantom{\rule{0.3em}{0ex}}\mathrm{a.u.})$ using an atomic orbital expansion technique. The elastic cross sections of these systems at thermal energies are found to be very high compared to $\overline{\mathrm{H}}\text{\ensuremath{-}}\mathrm{H}$ and $\overline{\mathrm{H}}\text{\ensuremath{-}}\mathrm{He}$ systems. The theoretical models employed in this study are so chosen to consider long-range forces dynamically in the calculation. The mechanism of cooling suggests that Li may be considered to be a good candidate as a buffer gas for enhanced cooling of antihydrogen atoms to ultracold temperature.
Projectile-elastic, target-elastic, and full close-coupling approximation models have been employed to investigate scattering of ortho-positronium off Li and Na atoms at low energies. Nine different basis sets for each system have been used to find the relative importance of atomic (target and projectile) states on the elastic scattering parameters and the convergence of the predicted results with added eigen- and pseudostates. The sss-wave elastic phase shifts, scattering lengths and cross sections of both the systems are reported upto the incident energy k=0.5a.u.k=0.5\phantom{\rule{0.3em}{0ex}}\text{a.u.}k=0.5a.u. and compared with the corresponding existing theoretical predictions. It has been found that the van der Waals and higher order long-range interactions play a crucial role in predicting sss-wave elastic parameters for Ps--alkali-metal-atom systems at low energies.
Interaction potentials for the X $^{1}\mathrm{\ensuremath{\Sigma}}_{\mathrm{g}}^{+}$ and a $^{3}\mathrm{\ensuremath{\Sigma}}_{\mathrm{u}}^{+}$ states of Li2{\mathrm{Li}}_{2}Li2​ are constructed and used in calculations of the elastic scattering of two 7Li^{7}\mathrm{Li}7Li atoms at ultralow temperatures. The extreme sensitivity of the cross sections to the details of the interaction potentials is demonstrated. The calculated elastic and spin-change cross sections are very large, of the order of ${10}^{\mathrm{\ensuremath{-}}13}$ cm2{\mathrm{cm}}^{2}cm2 at zero temperature. The predicted scattering length for the triplet state is negative with a value of -17.2a0{\mathit{a}}_{0}a0​. Pronounced shape resonances appear at energies of 4.9\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}8}$ a.u. in the singlet scattering and 5.5\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}7}$ a.u. in the triplet scattering.
Quantal calculations for scattering of ground-state antihydrogen by metastable (n=2S)(n=2S)(n=2S) helium atoms have been performed using the nonadiabatic, atomic orbital expansion technique at thermal energies. The zero-energy elastic cross sections of the present systems are much greater than the corresponding value for the ground-state helium target. The low-energy elastic cross section for the singlet metastable helium [He(21S)][\mathrm{He}(2\phantom{\rule{0.2em}{0ex}}^{1}S)][He(21S)] target is higher than the corresponding value when the target is in the metastable triplet state [He(23S)][\mathrm{He}(2\phantom{\rule{0.2em}{0ex}}^{3}S)][He(23S)].
We calculate the isotope-independent Li+{\mathrm{Li}}^{+}Li+-Li potential energy curves for the electronic ground and first excited states. The scattering phase shifts and total scattering cross section for the $^{7}\mathrm{Li}^{+}\text{\ensuremath{-}}^{7}\mathrm{Li}$ collision are calculated, with an emphasis on the ultralow-energy domain down to the sss-wave regime. The effect of physically motivated alterations on the calculated potential energy curves is used to determine the bound of accuracy of the low-energy scattering parameters for the ion-atom system. It is found that the scattering length for the $A{\phantom{\rule{0.16em}{0ex}}}^{2}{\mathrm{\ensuremath{\Sigma}}}_{u}^{+}$ state, au=1325a0{a}_{u}=1325{a}_{0}au​=1325a0​, is positive and has well-constrained bounds. For the $X{\phantom{\rule{0.16em}{0ex}}}^{2}{\mathrm{\ensuremath{\Sigma}}}_{g}^{+}$ state, the scattering length, ag=20465a0{a}_{g}=20\phantom{\rule{0.16em}{0ex}}465{a}_{0}ag​=20465a0​, has a large magnitude, as it is sensitive to the restrained change of the potential, due to the presence of a vibrational state in the vicinity of the dissociation limit.
Calculations have been carried out for the vibrational quenching of excited H(2) molecules which collide with Li(+) ions at ultralow energies. The dynamics has been treated exactly using the well-known quantum coupled-channel expansions over different initial vibrational levels. The overall interaction potential has been obtained from the calculations carried out earlier by our group using highly correlated ab initio methods. The results indicate that specific features of the scattering observables, e.g., the appearance of Ramsauer-Townsend minima in elastic channel cross sections and the marked increase of the cooling rates from specific initial states, can be linked to potential properties at vanishing energies (sign and size of scattering lengths) and to the presence of either virtual states or bound states. The suggestion is made such that by selecting the initial state preparation of the molecular partners, the ionic interactions would be amenable to controlling quenching efficiency at ultralow energies.