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 Chemistry Chemical Physics

N 2 + ( 2 Σ g ) and Rb( 2 S) in a hybrid trap: modeling ion losses from radiative association paths

Francesco Antonio Gianturco, Alexander Dörfler, Stefan Willitsch, Ersin Yurtsever, Tomás González‐Lezana, Pablo Villarreal

Published Jan 1, 2019• 7 citations
Publisher

Abstract

By employing ab initio computed intermolecular potential energy surfaces we calculate the radiative association probabilities and rates for two different associative mechanisms involving trapped molecular ions N2+(2Σg) interacting either directly with ultracold Rb atoms or undergoing charge-exchange (CE) processes leading to the formation of complexes of the strongly exothermic products N2(X1Σg) plus Rb+(1S0). The two processes are expected to provide possible paths to ion losses in the trap within the timescale of experiments. The present calculations suggest that the associative rates for the 'vibrational' direct process are too small to be of any significant importance at the millikelvin temperatures considered in the experiments, while the 'vibronic' path into radiatively associating the CE products has a probability of occurring which is several orders of magnitude larger. However the reaction rate constants attributed to non-adiabatic CE [F. H. J. Hall and S. Willist, Phys. Rev. Lett., 2012, 109, 233202] are in turn several orders of magnitude larger than the radiative ones calculated here, thereby making the primary experimental process substantially unaffected by the radiative losses channel.

DOI
10.1039/c8cp06761a

Related papers

Cold ion-neutral reactions

Felix H. J. Hall

Cold ion-neutral reactive processes were studied in an hybrid trap down to average collision energies <E_coll>/k_B > 20 mK. The atomic ion-neutral systems Ca^+ + Rb and Ba^+ + Rb were studied, and the results interpreted with high-level quantum chemical and quantum scattering calculations. Three reactive processes were found to be in competition, namely non-radiative charge transfer induced by non-adiabatic couplings between potential energy surfaces, radiative charge transfer, and radiative association of molecular ions, which were observed using mass spectrometry. The role of light in these processes was investigated. Enhancement of reaction rate constants from electronically excited entrance channels was observed and rationalised using computed potential energy curves. The collision-energy dependence of the reaction rate constants was investigated, and was found to be in line with predictions of both classical and quantum models uncovering general effects in cold ion-neutral systems. Cold reactions in the molecular ion-neutral system N_2^+ + Rb were also investigated with average collision energies two orders of magnitude lower than previously realised. The reaction rate constant in this system was found to depend strongly on the Rb ^2P_3/2 population, with the rate constant from the corresponding excited entrance channel being significantly faster than the collision rate predicted by Langevin theory. A classical capture model was developed taking into account the charge permanent-quadrupole intermolecular force and was found to reproduce the observed rate. The implied near unit reaction probability was rationalised by a near electronic resonance of entrance and product channels. A detailed description of the implementation of the ion-neutral hybrid trap is given. A thorough comparison of the results from state-of-the-art experiments and theory reveals general features of light assisted cold ion-neutral reactions. \n

•Jan 1, 2013•0 citations

Formation of molecular ions by radiative association of cold trapped atoms and ions

Humberto da Silva, Maurice Raoult, M Aymar +1 more

Radiative emission during cold collisions between trapped laser-cooled Rb atoms and alkaline-earth ions (Ca$^+$, Sr$^+$, Ba$^+$) and Yb$^+$, and between Li and Yb$^+$, are studied theoretically, using accurate effective-core-potential based quantum chemistry calculations of potential energy curves and transition dipole moments of the related molecular ions. Radiative association of molecular ions is predicted to occur for all systems with a cross section two to ten times larger than the radiative charge transfer one. Partial and total rate constants are also calculated and compared to available experiments. Narrow shape resonances are expected, which could be detectable at low temperature with an experimental resolution at the limit of the present standards. Vibrational distributions are also calculated, showing that the final molecular ions are not created in their ground state level.

•Feb 26, 2015•46 citations

Formation of molecular ions by radiative association of cold trapped atoms and ions

Humberto da Silva, Maurice Raoult, M Aymar +1 more

Radiative emission during cold collisions between trapped laser-cooled Rb atoms and alkaline-earth ions (Ca + , Sr + , Ba + ) and Yb + , and between Li and Yb + , are studied theoretically, using accurate effective core potential based quantum chemistry calculations of potential energy curves and transition dipole moments of the related molecular ions. Radiative association of molecular ions is predicted to occur for all systems with a cross section two to ten times larger than the radiative charge transfer one. Partial and total rate constants are also calculated and compared to available experiments. Narrow shape resonances are expected, which could be detectable at low temperature with an experimental resolution at the limit of the present standards. Vibrational distributions are also calculated, showing that the final molecular ions are not created in their ground state level.

arXiv:1501.06385•New Journal of Physics•Apr 23, 2015•53 citations

Ion-loss events in a hybrid trap of cold Rb-Ca+ : Photodissociation, blackbody radiation, and nonradiative charge exchange

Xiaodong Xing, Humberto da Silva, Romain Véxiau +3 more

We theoretically investigate the collisional dynamics of laser-cooled ${}^{87}\text{Rb}$ ground-state atoms and ${}^{40}{\mathrm{Ca}}^{+}$ ground-state ions in the context of the hybrid trap experiment of Hall et al. [Phys. Rev. Lett. 107, 243202 (2011)], leading to ion losses. Cold ${}^{87}{\mathrm{Rb}}^{40}{\mathrm{Ca}}^{+}$ ground-state molecular ions are created by radiative association, and we demonstrate that they are protected against photodissociation by blackbody radiation and by the ${}^{40}{\mathrm{Ca}}^{+}$ cooling laser at 397 nm. This paper yields an interpretation of the direct observation of ${}^{87}{\mathrm{Rb}}^{40}{\mathrm{Ca}}^{+}$ ions in the experiment, in contrast to other hybrid trap experiments using other species. Based on an updated model for molecular spin-orbit interaction, we also confirm that the nonradiative charge-exchange is the dominant loss process for ${\mathrm{Ca}}^{+}$ and obtain rates in agreement with experimental observations and a previous calculation.

arXiv:2209.08008•Physical Review A•Dec 8, 2022•9 citations

Ultracold, radiative charge transfer in hybrid Yb ion–Rb atom traps

B. M. McLaughlin, H D L Lamb, I C Lane +1 more

Ultracold hybrid ion–atom traps offer the possibility of microscopic manipulation of quantum coherences in the gas using the ion as a probe. However, inelastic processes, particularly charge transfer can be a significant process of ion loss and has been measured experimentally for the ion immersed in a Rb vapour. We use first-principles quantum chemistry codes to obtain the potential energy curves and dipole moments for the lowest-lying energy states of this complex. Calculations for the radiative decay processes cross sections and rate coefficients are presented for the total decay processes; and . Comparing the semi-classical Langevin approximation with the quantum approach, we find it provides a very good estimate of the background at higher energies. The results demonstrate that radiative decay mechanisms are important over the energy and temperature region considered. In fact, the Langevin process of ion–atom collisions dominates cold ion–atom collisions. For spin-dependent processes [ 1 ] the anisotropic magnetic dipole–dipole interaction and the second-order spin–orbit coupling can play important roles, inducing coupling between the spin and the orbital motion. They measured the spin-relaxing collision rate to be approximately five orders of magnitude higher than the charge-exchange collision rate [ 1 ]. Regarding the measured radiative charge transfer collision rate, we find that our calculation is in very good agreement with experiment and with previous calculations. Nonetheless, we find no broad resonances features that might underly a strong isotope effect. In conclusion, we find, in agreement with previous theory that the isotope anomaly observed in experiment remains an open question.

arXiv:1404.6579•Journal of Physics B Atomic Molecular and Optical Physics•Jul 4, 2014•20 citations

Charge Exchange Dynamics in Cold Collisions of 40CaH+ and 39K

Swapnil Patel, Dibyendu Sardar, Jyothi Saraladevi +2 more

Abstract We report the observation of charge-exchange collisions between trapped calcium monohydride molecular ions (40CaH+) and ultracold potassium atoms (39K) in a hybrid ion-atom trap. The measured charge-exchange rate coefficient is significantly suppressed relative to the Langevin rate constant for the system. We use ab initio quantum-chemical calculations to model the (CaH-K)+ complex in the ground and excited electronic states and to identify possible charge-exchange mechanisms. Our calculations rule out a direct nonradiative charge-exchange reaction and instead point to a radiative mechanism, but do not quantitatively reproduce the measured rate, highlighting the need for a full-dimensional quantum dynamics treatment that includes vibrational motion and intermediate complex formation. Our work demonstrates that cold hybrid ion-atom platforms with molecular ions enable access to richer chemical complexity and collisional dynamics inaccessible in purely atomic systems.

arXiv:2602.09142•The Journal of Physical Chemistry Letters•Jun 3, 2026•0 citations
By employing ab initio computed intermolecular potential energy surfaces we calculate the radiative association probabilities and rates for two different associative mechanisms involving trapped molecular ions N2+(2Σg) interacting either directly with ultracold Rb atoms or undergoing charge-exchange (CE) processes leading to the formation of complexes of the strongly exothermic products N2(X1Σg) plus Rb+(1S0). The two processes are expected to provide possible paths to ion losses in the trap within the timescale of experiments. The present calculations suggest that the associative rates for the 'vibrational' direct process are too small to be of any significant importance at the millikelvin temperatures considered in the experiments, while the 'vibronic' path into radiatively associating the CE products has a probability of occurring which is several orders of magnitude larger. However the reaction rate constants attributed to non-adiabatic CE [F. H. J. Hall and S. Willist, Phys. Rev. Lett., 2012, 109, 233202] are in turn several orders of magnitude larger than the radiative ones calculated here, thereby making the primary experimental process substantially unaffected by the radiative losses channel.
Cold ion-neutral reactive processes were studied in an hybrid trap down to average collision energies <E_coll>/k_B > 20 mK. The atomic ion-neutral systems Ca^+ + Rb and Ba^+ + Rb were studied, and the results interpreted with high-level quantum chemical and quantum scattering calculations. Three reactive processes were found to be in competition, namely non-radiative charge transfer induced by non-adiabatic couplings between potential energy surfaces, radiative charge transfer, and radiative association of molecular ions, which were observed using mass spectrometry. The role of light in these processes was investigated. Enhancement of reaction rate constants from electronically excited entrance channels was observed and rationalised using computed potential energy curves. The collision-energy dependence of the reaction rate constants was investigated, and was found to be in line with predictions of both classical and quantum models uncovering general effects in cold ion-neutral systems. Cold reactions in the molecular ion-neutral system N_2^+ + Rb were also investigated with average collision energies two orders of magnitude lower than previously realised. The reaction rate constant in this system was found to depend strongly on the Rb ^2P_3/2 population, with the rate constant from the corresponding excited entrance channel being significantly faster than the collision rate predicted by Langevin theory. A classical capture model was developed taking into account the charge permanent-quadrupole intermolecular force and was found to reproduce the observed rate. The implied near unit reaction probability was rationalised by a near electronic resonance of entrance and product channels. A detailed description of the implementation of the ion-neutral hybrid trap is given. A thorough comparison of the results from state-of-the-art experiments and theory reveals general features of light assisted cold ion-neutral reactions. \n
Radiative emission during cold collisions between trapped laser-cooled Rb atoms and alkaline-earth ions (Ca+^++, Sr+^++, Ba+^++) and Yb+^++, and between Li and Yb+^++, are studied theoretically, using accurate effective-core-potential based quantum chemistry calculations of potential energy curves and transition dipole moments of the related molecular ions. Radiative association of molecular ions is predicted to occur for all systems with a cross section two to ten times larger than the radiative charge transfer one. Partial and total rate constants are also calculated and compared to available experiments. Narrow shape resonances are expected, which could be detectable at low temperature with an experimental resolution at the limit of the present standards. Vibrational distributions are also calculated, showing that the final molecular ions are not created in their ground state level.
Radiative emission during cold collisions between trapped laser-cooled Rb atoms and alkaline-earth ions (Ca + , Sr + , Ba + ) and Yb + , and between Li and Yb + , are studied theoretically, using accurate effective core potential based quantum chemistry calculations of potential energy curves and transition dipole moments of the related molecular ions. Radiative association of molecular ions is predicted to occur for all systems with a cross section two to ten times larger than the radiative charge transfer one. Partial and total rate constants are also calculated and compared to available experiments. Narrow shape resonances are expected, which could be detectable at low temperature with an experimental resolution at the limit of the present standards. Vibrational distributions are also calculated, showing that the final molecular ions are not created in their ground state level.
We theoretically investigate the collisional dynamics of laser-cooled 87Rb{}^{87}\text{Rb}87Rb ground-state atoms and 40Ca+{}^{40}{\mathrm{Ca}}^{+}40Ca+ ground-state ions in the context of the hybrid trap experiment of Hall et al. [Phys. Rev. Lett. 107, 243202 (2011)], leading to ion losses. Cold 87Rb40Ca+{}^{87}{\mathrm{Rb}}^{40}{\mathrm{Ca}}^{+}87Rb40Ca+ ground-state molecular ions are created by radiative association, and we demonstrate that they are protected against photodissociation by blackbody radiation and by the 40Ca+{}^{40}{\mathrm{Ca}}^{+}40Ca+ cooling laser at 397 nm. This paper yields an interpretation of the direct observation of 87Rb40Ca+{}^{87}{\mathrm{Rb}}^{40}{\mathrm{Ca}}^{+}87Rb40Ca+ ions in the experiment, in contrast to other hybrid trap experiments using other species. Based on an updated model for molecular spin-orbit interaction, we also confirm that the nonradiative charge-exchange is the dominant loss process for Ca+{\mathrm{Ca}}^{+}Ca+ and obtain rates in agreement with experimental observations and a previous calculation.
Ultracold hybrid ion–atom traps offer the possibility of microscopic manipulation of quantum coherences in the gas using the ion as a probe. However, inelastic processes, particularly charge transfer can be a significant process of ion loss and has been measured experimentally for the ion immersed in a Rb vapour. We use first-principles quantum chemistry codes to obtain the potential energy curves and dipole moments for the lowest-lying energy states of this complex. Calculations for the radiative decay processes cross sections and rate coefficients are presented for the total decay processes; and . Comparing the semi-classical Langevin approximation with the quantum approach, we find it provides a very good estimate of the background at higher energies. The results demonstrate that radiative decay mechanisms are important over the energy and temperature region considered. In fact, the Langevin process of ion–atom collisions dominates cold ion–atom collisions. For spin-dependent processes [ 1 ] the anisotropic magnetic dipole–dipole interaction and the second-order spin–orbit coupling can play important roles, inducing coupling between the spin and the orbital motion. They measured the spin-relaxing collision rate to be approximately five orders of magnitude higher than the charge-exchange collision rate [ 1 ]. Regarding the measured radiative charge transfer collision rate, we find that our calculation is in very good agreement with experiment and with previous calculations. Nonetheless, we find no broad resonances features that might underly a strong isotope effect. In conclusion, we find, in agreement with previous theory that the isotope anomaly observed in experiment remains an open question.
Abstract We report the observation of charge-exchange collisions between trapped calcium monohydride molecular ions (40CaH+) and ultracold potassium atoms (39K) in a hybrid ion-atom trap. The measured charge-exchange rate coefficient is significantly suppressed relative to the Langevin rate constant for the system. We use ab initio quantum-chemical calculations to model the (CaH-K)+ complex in the ground and excited electronic states and to identify possible charge-exchange mechanisms. Our calculations rule out a direct nonradiative charge-exchange reaction and instead point to a radiative mechanism, but do not quantitatively reproduce the measured rate, highlighting the need for a full-dimensional quantum dynamics treatment that includes vibrational motion and intermediate complex formation. Our work demonstrates that cold hybrid ion-atom platforms with molecular ions enable access to richer chemical complexity and collisional dynamics inaccessible in purely atomic systems.