Limits...
Explanation of efficient quenching of molecular ion vibrational motion by ultracold atoms.

Stoecklin T, Halvick P, Gannouni MA, Hochlaf M, Kotochigova S, Hudson ER - Nat Commun (2016)

Bottom Line: Here, we theoretically explain the recently observed exception to this rule: efficient vibrational cooling of BaCl(+) by a laser-cooled Ca buffer gas.We perform intense close-coupling calculations that agree with the experimental result, and use both quantum defect theory and a statistical capture model to provide an intuitive understanding of the system.This result establishes that, in contrast to the commonly held opinion, there exists a large class of systems that exhibit efficient vibrational cooling and therefore supports a new route to realize the long-sought opportunities offered by molecular structure.

View Article: PubMed Central - PubMed

Affiliation: Université de Bordeaux, Institut des Sciences Moléculaires, UMR 5255 CNRS, 33405 Talence, France.

ABSTRACT
Buffer gas cooling of molecules to cold and ultracold temperatures is a promising technique for realizing a host of scientific and technological opportunities. Unfortunately, experiments using cryogenic buffer gases have found that although the molecular motion and rotation are quickly cooled, the molecular vibration relaxes at impractically long timescales. Here, we theoretically explain the recently observed exception to this rule: efficient vibrational cooling of BaCl(+) by a laser-cooled Ca buffer gas. We perform intense close-coupling calculations that agree with the experimental result, and use both quantum defect theory and a statistical capture model to provide an intuitive understanding of the system. This result establishes that, in contrast to the commonly held opinion, there exists a large class of systems that exhibit efficient vibrational cooling and therefore supports a new route to realize the long-sought opportunities offered by molecular structure.

No MeSH data available.


Related in: MedlinePlus

Quantum defect theory (QDT) for previously studied systems.Ratio of the thermalized elastic and loss rate coefficients, Kelastic/Kloss, as function of temperature for the N2++He (dashed line) and CH++He (solid line) systems using optimized QDT.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4837476&req=5

f6: Quantum defect theory (QDT) for previously studied systems.Ratio of the thermalized elastic and loss rate coefficients, Kelastic/Kloss, as function of temperature for the N2++He (dashed line) and CH++He (solid line) systems using optimized QDT.

Mentions: Traditional cooling schemes often involve collisions of ionic molecules with He gas at cryogenic temperatures. Here, we analyse the ratio Kelastic/Kloss for two ionic systems He-N2+ and He-CH+ to demonstrate a different cooling mechanism than for cooling with Ca. First, we fit the He-N2+ and He-CH+ vibrational quenching rate coefficients obtained in the coupled-channel calculations1012 to our QDT theory with partial wave-dependent short-range parameters. The parameters of our best fit are η0=1–5.7*10−6, η1=−2*10−6, δℓm(E)=0.76π for He-N2+ and η0=1–7*10−3, η1=0 and δℓm(E)=0.06π for He-CH+. Figure 6 shows the temperature-dependent ratio Kelastic/Kloss for these two systems. It is evident that for both systems the elastic rate coefficient is much larger than that of the inelastic processes. Hence, for a molecular ion in a given excited rovibrational level its translational motion will be cooled first. Occasionally, an inelastic process relaxes this internal state at the cost of rapid increase of the translational temperature. Elastic collisions will then start the cooling all over again.


Explanation of efficient quenching of molecular ion vibrational motion by ultracold atoms.

Stoecklin T, Halvick P, Gannouni MA, Hochlaf M, Kotochigova S, Hudson ER - Nat Commun (2016)

Quantum defect theory (QDT) for previously studied systems.Ratio of the thermalized elastic and loss rate coefficients, Kelastic/Kloss, as function of temperature for the N2++He (dashed line) and CH++He (solid line) systems using optimized QDT.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837476&req=5

f6: Quantum defect theory (QDT) for previously studied systems.Ratio of the thermalized elastic and loss rate coefficients, Kelastic/Kloss, as function of temperature for the N2++He (dashed line) and CH++He (solid line) systems using optimized QDT.
Mentions: Traditional cooling schemes often involve collisions of ionic molecules with He gas at cryogenic temperatures. Here, we analyse the ratio Kelastic/Kloss for two ionic systems He-N2+ and He-CH+ to demonstrate a different cooling mechanism than for cooling with Ca. First, we fit the He-N2+ and He-CH+ vibrational quenching rate coefficients obtained in the coupled-channel calculations1012 to our QDT theory with partial wave-dependent short-range parameters. The parameters of our best fit are η0=1–5.7*10−6, η1=−2*10−6, δℓm(E)=0.76π for He-N2+ and η0=1–7*10−3, η1=0 and δℓm(E)=0.06π for He-CH+. Figure 6 shows the temperature-dependent ratio Kelastic/Kloss for these two systems. It is evident that for both systems the elastic rate coefficient is much larger than that of the inelastic processes. Hence, for a molecular ion in a given excited rovibrational level its translational motion will be cooled first. Occasionally, an inelastic process relaxes this internal state at the cost of rapid increase of the translational temperature. Elastic collisions will then start the cooling all over again.

Bottom Line: Here, we theoretically explain the recently observed exception to this rule: efficient vibrational cooling of BaCl(+) by a laser-cooled Ca buffer gas.We perform intense close-coupling calculations that agree with the experimental result, and use both quantum defect theory and a statistical capture model to provide an intuitive understanding of the system.This result establishes that, in contrast to the commonly held opinion, there exists a large class of systems that exhibit efficient vibrational cooling and therefore supports a new route to realize the long-sought opportunities offered by molecular structure.

View Article: PubMed Central - PubMed

Affiliation: Université de Bordeaux, Institut des Sciences Moléculaires, UMR 5255 CNRS, 33405 Talence, France.

ABSTRACT
Buffer gas cooling of molecules to cold and ultracold temperatures is a promising technique for realizing a host of scientific and technological opportunities. Unfortunately, experiments using cryogenic buffer gases have found that although the molecular motion and rotation are quickly cooled, the molecular vibration relaxes at impractically long timescales. Here, we theoretically explain the recently observed exception to this rule: efficient vibrational cooling of BaCl(+) by a laser-cooled Ca buffer gas. We perform intense close-coupling calculations that agree with the experimental result, and use both quantum defect theory and a statistical capture model to provide an intuitive understanding of the system. This result establishes that, in contrast to the commonly held opinion, there exists a large class of systems that exhibit efficient vibrational cooling and therefore supports a new route to realize the long-sought opportunities offered by molecular structure.

No MeSH data available.


Related in: MedlinePlus