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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

Potential energy.(a) Contour plot of the total PES for θ=55°. Contour energies are regularly spaced by 1,000 cm−1. (b) Contour plot of the three-body interaction energy for r=5 a0. Below −500 cm−1, contour energies are regularly spaced by 500 cm−1. Red contours correspond to positive energies, and blue to zero and negative energies.
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f1: Potential energy.(a) Contour plot of the total PES for θ=55°. Contour energies are regularly spaced by 1,000 cm−1. (b) Contour plot of the three-body interaction energy for r=5 a0. Below −500 cm−1, contour energies are regularly spaced by 500 cm−1. Red contours correspond to positive energies, and blue to zero and negative energies.

Mentions: The results of these calculations are shown in Fig. 1 along two dimensions in the Jacobi space. Figure 1a shows the existence of a relatively deep potential well in good agreement with the charge-transfer nature of the bonding within this ionic complex. Figure 1b reveals the existence of two minimal structures and two saddle points connecting these equilibrium structures. It also shows that the potential is strongly anisotropic. Although the Ba–Cl bond length is only slightly extended by the interaction with the calcium, we observe in Fig. 1a that the vibrational potential of BaCl+ is significantly modified by the latter interaction. This indicates there is a significant coupling between the vibration of BaCl+ and the other modes of motion. This coupling is expected to promote vibrationally inelastic collisions.


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)

Potential energy.(a) Contour plot of the total PES for θ=55°. Contour energies are regularly spaced by 1,000 cm−1. (b) Contour plot of the three-body interaction energy for r=5 a0. Below −500 cm−1, contour energies are regularly spaced by 500 cm−1. Red contours correspond to positive energies, and blue to zero and negative energies.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Potential energy.(a) Contour plot of the total PES for θ=55°. Contour energies are regularly spaced by 1,000 cm−1. (b) Contour plot of the three-body interaction energy for r=5 a0. Below −500 cm−1, contour energies are regularly spaced by 500 cm−1. Red contours correspond to positive energies, and blue to zero and negative energies.
Mentions: The results of these calculations are shown in Fig. 1 along two dimensions in the Jacobi space. Figure 1a shows the existence of a relatively deep potential well in good agreement with the charge-transfer nature of the bonding within this ionic complex. Figure 1b reveals the existence of two minimal structures and two saddle points connecting these equilibrium structures. It also shows that the potential is strongly anisotropic. Although the Ba–Cl bond length is only slightly extended by the interaction with the calcium, we observe in Fig. 1a that the vibrational potential of BaCl+ is significantly modified by the latter interaction. This indicates there is a significant coupling between the vibration of BaCl+ and the other modes of motion. This coupling is expected to promote vibrationally inelastic collisions.

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