Showing papers by "Robin Côté published in 2003"
TL;DR: In this article, the authors present evidence for molecular resonances in a cold dense gas of rubidium Rydberg atoms, and attribute these normally forbidden transitions to avoided crossings between the long-range molecular potentials of two rydberg atom pairs.
Abstract: We present evidence for molecular resonances in a cold dense gas of rubidium Rydberg atoms. Single UV photon excitation from the $5s$ ground state to $np$ Rydberg states ($n=50\char21{}90$) reveals resonances at energies corresponding to excited atom pairs $(n\ensuremath{-}1)d+ns$. We attribute these normally forbidden transitions to avoided crossings between the long-range molecular potentials of two Rydberg atoms. These strong van der Waals interactions result in avoided crossings at extremely long range, e.g., $\ensuremath{\sim}58\text{ }000$ times the Bohr radius (${a}_{0})$ for $n=70$.
95 citations
TL;DR: In this paper, the authors studied the collisional cooling of laser precooled Ca{sup +} ions by ultracold Na atoms and calculated the potential curves using complete active space self-consistent field and Moeller-Plesset second-order perturbation theory.
Abstract: New experiments were proposed recently to investigate the regime of cold atomic and molecular ion-atom collision processes in a special hybrid neutral-atom-ion trap under high-vacuum conditions. We study the collisional cooling of laser precooled Ca{sup +} ions by ultracold Na atoms. Modeling this process requires knowledge of the radiative lifetime of the excited singlet A {sup 1}{sigma}{sup +} state of the (NaCa){sup +} molecular system. We calculate the rate coefficient for radiative charge transfer using a semiclassical approach. The dipole radial matrix elements between the ground and the excited states, and the potential curves were calculated using complete active space self-consistent field and Moeller-Plesset second-order perturbation theory with an extended Gaussian basis, 6-311+G (3df). The semiclassical charge-transfer rate coefficient was averaged over a thermal Maxwellian distribution. In addition, we also present elastic collision cross sections and the spin-exchange cross section. The rate coefficient for charge transfer was found to be 2.3x10{sup -16} cm{sup 3}/sec, while those for the elastic and spin-exchange cross sections were found to be several orders of magnitude higher (1.1x10{sup -8} cm{sup 3}/sec and 2.3x10{sup -9} cm{sup 3}/sec, respectively). This confirms our assumption that the milli-Kelvin regime of collisional cooling of calcium ions by sodium atoms ismore » favorable with the respect to low loss of calcium ions due to the charge transfer.« less
88 citations
01 May 2003
TL;DR: In this paper, spectral evidence for long-range molecular resonances involving pairs of cold Rydberg atoms is presented. And they attribute these features to avoided crossings between Ryd Berg-Rydberg long-term molecular interaction potentials.
Abstract: We have seen spectral evidence for long-range molecular resonances involving pairs of cold Rydberg atoms. We attribute these features to avoided crossings between Rydberg-Rydberg long-range molecular interaction potentials.
21 citations
TL;DR: In this paper, the design of atom-optic components, such as mirrors, to manipulate ultracold atoms was explored, and it was shown that it is possible to enhance significantly quantum effects by engineering sharp features in the interaction potential between atoms and the component.
Abstract: We explore the design of atom-optic components, such as mirrors, to manipulate ultracold atoms. We show that it is possible to enhance significantly quantum effects by engineering sharp features in the interaction potential between atoms and the component. We illustrate the concept by calculating the reflection probability for ultracold sodium atoms incident on a bichromatic evanescent-wave atomic mirror created by lasers red and blue detuned from resonance with intensities and detunings chosen to enhance quantum reflection of a purely attractive potential. With realistic parameters for sodium atoms incident on glass at 10 cm/s, up to 30% reflection can be obtained.
12 citations
01 Jan 2003
TL;DR: In this paper, the potentials for collisions of one-electron Ca+ ions with co-trapped Na atoms suggest the excited (triplet sigma +) state of (NaCa)+ is metastable with respect to charge transfer.
Abstract: Calculated potentials for collisions of one-electron Ca+ ions with co-trapped Na atoms suggest the excited (triplet sigma +) state of (NaCa)+ is metastable with respect to charge transfer. Measurements of the elastic cross sections for cooling of Ca+ and of internally hot Na molecular ions by ultracold Na are planned.
9 citations
06 Jun 2003
TL;DR: In this paper, spectral evidence for long-range molecular resonances involving pairs of cold Rydberg atoms is presented. And they attribute these features to avoided crossings between Ryd Berg-Rydberg long-term molecular interaction potentials.
Abstract: We have seen spectral evidence for long-range molecular resonances involving pairs of cold Rydberg atoms. We attribute these features to avoided crossings between Rydberg-Rydberg long-range molecular interaction potentials.
4 citations
TL;DR: In this article, a two-photon Raman probe is used to obtain line shapes which reveal properties of the degenerate sample, notably its temperature T. The proposed method could be used with identical fermions in different hyperfine states interacting via s-wave scattering or identical fermanions in the same hyperfine state via pwave scattering.
Abstract: We suggest a simple method for measuring the temperature of ultracold gases made of fermions. We show that by using a two-photon Raman probe, it is possible to obtain line shapes which reveal properties of the degenerate sample, notably its temperature T. The proposed method could be used with identical fermions in different hyperfine states interacting via s-wave scattering or identical fermions in the same hyperfine state via p-wave scattering. We illustrate the applicability of the method in realistic conditions for {sup 6}Li prepared in two different hyperfine states. We find that temperatures down to 0.05T{sub F} can be determined by this in situ method.
1 citations
01 May 2003
TL;DR: In this paper, a two-photon Raman probe is used to obtain line shapes which reveal properties of the degenerate sample, notably its temperature T. The proposed method could be used with identical fermions in different hyperfine states interacting via s-wave scattering or identical fermanions in the same hyperfine state via pwave scattering.
Abstract: We suggest a simple method for measuring the temperature of ultracold gases made of fermions. We show that by using a two-photon Raman probe, it is possible to obtain line shapes which reveal properties of the degenerate sample, notably its temperature T. The proposed method could be used with identical fermions in different hyperfine states interacting via s-wave scattering or identical fermions in the same hyperfine state via p-wave scattering. We illustrate the applicability of the method in realistic conditions for {sup 6}Li prepared in two different hyperfine states. We find that temperatures down to 0.05T{sub F} can be determined by this in situ method.