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

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Trapping cold molecules

Robert deCarvalho, Jonathan D. Weinstein, Břetislav Friedrich, John M. Doyle

Published Mar 29, 2002• 3 citations
Publisher

Abstract

An experiment is described in which 108 CaH molecules have been confined in a magnetic trap at a temperature of 400 mK. The elastic scattering cross section of CaH on 3He was measured to be σelequals(1.5±0.6)×10-14cm2. A lower bound of Γrotational⩾10-15cm3s-1 was placed on the rotational elastic collision rate coefficient, and an upper bound of Γν<10-15 cm3s-1 was placed on the vibrational relaxation rate coefficient. The rate coefficient for spin changing collisions was measured to be, within an order magnitude, Γ Zequals10-17 cm3 s-1.

DOI
10.1117/12.463837

Related papers

The He–CaH(2Σ+) interaction. II. Collisions at cold and ultracold temperatures

N. Balakrishnan, Gerrit C. Groenenboom, Roman V. Krems +1 more

We present cross sections for rotational, vibrational, and fine-structure transitions in He–CaH(2Σ) collisions at cold and ultracold temperatures calculated using the ab initio potential energy surface reported in the preceding paper. Rotational quenching is fast, vibrational quenching is slow. The spin-rotational interaction, although small and having no influence at temperatures above 10 K, changes significantly the rate coefficients for rotational quenching at lower temperatures. The theoretical rotational, vibrational, and elastic cross sections are compared with the results of a buffer gas cooling experiment carried out at a temperature of about 0.4 K. The theoretical predictions for the vibrational and elastic cross sections are larger than the measured values. The sensitivity to the potential energy surface is explored. A modified surface diminishes but does not remove the differences between theory and experiment.

The Journal of Chemical Physics•Apr 11, 2003•80 citations

Inelastic collisions of CaH with He at cryogenic temperatures

Vijay Singh, Kyle S. Hardman, Mei-Ju Lu +3 more

Using helium buffer gas cooling, we have prepared dense samples of ground-state molecular calcium monohydride (CaH X 2Σ) at cryogenic temperatures. We have used optical pumping to polarise the spin state of the CaH molecules and we have measured the inelastic collisions of molecular CaH with atomic helium at temperatures from 2 to 7 K. The measured CaH electronic spin depolarisation rate coefficient increases rapidly with increasing temperature, increasing from 2 × 10−13 cm3 s−1 to over 10−11 cm3 s−1. The strong dependence of rate coefficient on temperature is attributed to the CaH population in the first excited rotational state.

Molecular Physics•Jun 13, 2013•9 citations

Cold N+NH Collisions in a Magnetic Trap

Matthew T. Hummon, Timur V. Tscherbul, Jacek A. Kłos +5 more

We present an experimental and theoretical study of atom-molecule collisions in a mixture of cold, trapped N atoms and NH molecules at a temperature of $\ensuremath{\sim}600\text{ }\text{ }\mathrm{mK}$. We measure a small $\mathrm{N}+\mathrm{NH}$ trap loss rate coefficient of ${k}_{\mathrm{loss}}^{(\mathrm{N}+\mathrm{NH})}=9(5)(3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$. Accurate quantum scattering calculations based on ab initio interaction potentials are in agreement with experiment and indicate the magnetic dipole interaction to be the dominant loss mechanism. Our theory further indicates the ratio of $\mathrm{N}+\mathrm{NH}$ elastic-to-inelastic collisions remains large ($>100$) into the mK regime.

arXiv:1009.2513•Physical Review Letters•Feb 2, 2011•91 citations

Rotational relaxation in ultracold He+BH collisions

Ming-Yan Gong, Xiaotao Xu, Eryin Feng

Collisions of cold and ultracold BH in the ν = 0 level with the He atom are investigated using the quantum mechanical scattering formulation. The elastic and the inelastic cross sections are calculated using the two-dimensional ab initio potential energy surface. It is shown that the elastic cross section is larger than the inelastic one. When the collision energy is very low, the elastic cross section follows the Wigner threshold law and is one order of magnitude larger than that of He-O 2 , while it is much smaller than that of He-H 2 . The efficiency of the rotationally quenching state is given. The Δ j = −1 transition is most efficient. The resonances are also found to occur at about the same translational energy (0.1–1 cm −1 ), which gives rise to steps in the rate coefficient at temperatures around 0.1–1 K.

Chinese Physics B•Nov 1, 2011•1 citation

Mechanism of Collisional Spin Relaxation in Σ3 Molecules

Wesley C. Campbell, Timur V. Tscherbul, Hsin-I Lu +3 more

We measure and theoretically determine the effect of molecular rotational splitting on Zeeman relaxation rates in collisions of cold 3Sigma molecules with helium atoms in a magnetic field. All four stable isotopomers of the imidogen (NH) molecule are magnetically trapped and studied in collisions with 3He and 4He. The 4He data support the predicted 1/B_{e};{2} dependence of the collision-induced Zeeman relaxation rate coefficient on the molecular rotational constant B_{e}. The measured 3He rate coefficients are much larger than the 4He coefficients, depend less strongly on B_{e}, and theoretical analysis indicates they are strongly affected by a shape resonance. The results demonstrate the influence of molecular structure on collisional energy transfer at low temperatures.

arXiv:0804.0265•Physical Review Letters•Jan 6, 2009•53 citations

Magnetic Trapping and Zeeman Relaxation of NH ( X Σ−3 )

Wesley C. Campbell, Edem Tsikata, Hsin-I Lu +2 more

NH radicals are magnetically trapped and their Zeeman relaxation and energy transport collision cross sections with helium are measured. Continuous buffer-gas loading of the trap is direct from a room-temperature molecular beam. The Zeeman relaxation (inelastic) cross section of magnetically trapped electronic, vibrational, and rotational ground state NH molecules in collisions with $^{3}\mathrm{He}$ is measured to be $3.8\ifmmode\pm\else\textpm\fi{}1.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}19}\text{ }\text{ }{\mathrm{cm}}^{2}$ at 710 mK. The NH-He energy transport cross section is also measured, indicating a ratio of diffusive to inelastic cross sections of $\ensuremath{\gamma}=7\ifmmode\times\else\texttimes\fi{}{10}^{4}$, in agreement with recent theory [R. V. Krems, H. R. Sadeghpour, A. Dalgarno, D. Zgid, J. K\l{}os, and G. Cha\l{}asi\ifmmode \acute{n}\else \'{n}\fi{}ski, Phys. Rev. A 68, 051401 (2003)].

arXiv:physics/0702071•Physical Review Letters•May 25, 2007•131 citations
An experiment is described in which 108 CaH molecules have been confined in a magnetic trap at a temperature of 400 mK. The elastic scattering cross section of CaH on 3He was measured to be σelequals(1.5±0.6)×10-14cm2. A lower bound of Γrotational⩾10-15cm3s-1 was placed on the rotational elastic collision rate coefficient, and an upper bound of Γν<10-15 cm3s-1 was placed on the vibrational relaxation rate coefficient. The rate coefficient for spin changing collisions was measured to be, within an order magnitude, Γ Zequals10-17 cm3 s-1.
We present cross sections for rotational, vibrational, and fine-structure transitions in He–CaH(2Σ) collisions at cold and ultracold temperatures calculated using the ab initio potential energy surface reported in the preceding paper. Rotational quenching is fast, vibrational quenching is slow. The spin-rotational interaction, although small and having no influence at temperatures above 10 K, changes significantly the rate coefficients for rotational quenching at lower temperatures. The theoretical rotational, vibrational, and elastic cross sections are compared with the results of a buffer gas cooling experiment carried out at a temperature of about 0.4 K. The theoretical predictions for the vibrational and elastic cross sections are larger than the measured values. The sensitivity to the potential energy surface is explored. A modified surface diminishes but does not remove the differences between theory and experiment.
Using helium buffer gas cooling, we have prepared dense samples of ground-state molecular calcium monohydride (CaH X 2Σ) at cryogenic temperatures. We have used optical pumping to polarise the spin state of the CaH molecules and we have measured the inelastic collisions of molecular CaH with atomic helium at temperatures from 2 to 7 K. The measured CaH electronic spin depolarisation rate coefficient increases rapidly with increasing temperature, increasing from 2 × 10−13 cm3 s−1 to over 10−11 cm3 s−1. The strong dependence of rate coefficient on temperature is attributed to the CaH population in the first excited rotational state.
We present an experimental and theoretical study of atom-molecule collisions in a mixture of cold, trapped N atoms and NH molecules at a temperature of $\ensuremath{\sim}600\text{ }\text{ }\mathrm{mK}$. We measure a small N+NH\mathrm{N}+\mathrm{NH}N+NH trap loss rate coefficient of ${k}_{\mathrm{loss}}^{(\mathrm{N}+\mathrm{NH})}=9(5)(3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$. Accurate quantum scattering calculations based on ab initio interaction potentials are in agreement with experiment and indicate the magnetic dipole interaction to be the dominant loss mechanism. Our theory further indicates the ratio of N+NH\mathrm{N}+\mathrm{NH}N+NH elastic-to-inelastic collisions remains large (>100>100>100) into the mK regime.
Collisions of cold and ultracold BH in the ν = 0 level with the He atom are investigated using the quantum mechanical scattering formulation. The elastic and the inelastic cross sections are calculated using the two-dimensional ab initio potential energy surface. It is shown that the elastic cross section is larger than the inelastic one. When the collision energy is very low, the elastic cross section follows the Wigner threshold law and is one order of magnitude larger than that of He-O 2 , while it is much smaller than that of He-H 2 . The efficiency of the rotationally quenching state is given. The Δ j = −1 transition is most efficient. The resonances are also found to occur at about the same translational energy (0.1–1 cm −1 ), which gives rise to steps in the rate coefficient at temperatures around 0.1–1 K.
We measure and theoretically determine the effect of molecular rotational splitting on Zeeman relaxation rates in collisions of cold 3Sigma molecules with helium atoms in a magnetic field. All four stable isotopomers of the imidogen (NH) molecule are magnetically trapped and studied in collisions with 3He and 4He. The 4He data support the predicted 1/B_{e};{2} dependence of the collision-induced Zeeman relaxation rate coefficient on the molecular rotational constant B_{e}. The measured 3He rate coefficients are much larger than the 4He coefficients, depend less strongly on B_{e}, and theoretical analysis indicates they are strongly affected by a shape resonance. The results demonstrate the influence of molecular structure on collisional energy transfer at low temperatures.
NH radicals are magnetically trapped and their Zeeman relaxation and energy transport collision cross sections with helium are measured. Continuous buffer-gas loading of the trap is direct from a room-temperature molecular beam. The Zeeman relaxation (inelastic) cross section of magnetically trapped electronic, vibrational, and rotational ground state NH molecules in collisions with 3He^{3}\mathrm{He}3He is measured to be $3.8\ifmmode\pm\else\textpm\fi{}1.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}19}\text{ }\text{ }{\mathrm{cm}}^{2}$ at 710 mK. The NH-He energy transport cross section is also measured, indicating a ratio of diffusive to inelastic cross sections of $\ensuremath{\gamma}=7\ifmmode\times\else\texttimes\fi{}{10}^{4}$, in agreement with recent theory [R. V. Krems, H. R. Sadeghpour, A. Dalgarno, D. Zgid, J. K\l{}os, and G. Cha\l{}asi\ifmmode \acute{n}\else \'{n}\fi{}ski, Phys. Rev. A 68, 051401 (2003)].