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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 7113-7125 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Theoretical calculations for the ground state and for 83 excited states of the Na2 molecule are presented in the framework of two independent approaches. The electron–core interaction is represented either by a pseudopotential or by a model potential, and a core polarization potential is introduced in both cases. The basis set contains either Gaussian orbitals or two-center generalized Slater orbitals. The two methods appear to give similar results, one being more accurate for the ground and first excited states, the other being better adapted to the intermediate Rydberg states. A very good agreement is obtained with the experimental spectroscopic constants determined for 26 states, the mean deviation being ΔRe=0.05a0, Δωe=0.86 cm−1, and ΔDe=57 cm−1.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-6079
    Keywords: PACS. 32.80.Pj Optical cooling of atoms; trapping - 33.80.Ps Optical cooling of molecules; trapping - 34.50.Rk Laser-modified scattering and reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Using a technique that consists in ionizing atoms out of the 5P 1/2 fragments originated in the cold collision process, we have measured the contribution of the fine structure changing collision (FS) to the total trap loss rate of cold 85Rb. Our results show that FS contribution is responsible for about 4% of the total trap loss. This result should stimulate new theoretical discussions involving exoergic cold collisions.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 13 (1989), S. 9-16 
    ISSN: 1434-6079
    Keywords: 31.20.T ; 32.80.D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A correlated wave function method, already used for two-electron molecular systems is extended here to the case of two-electron atomic systems. A careful investigation of some exact properties of the wave function is performed (Kato's conditions, Fock's development, fulfilment of the virial theorem), showing its good behaviour at small interelectronic distances or in strongly correlated states. The application to Helium and H− doubly-excited states is developed as a preliminary case of a more general study concerned with alkali-negative ions featuring in the second paper of this series. Energies and some autoionizing widths of He and H− are calculated. Given the simplicity of our model, close agreement is found in all cases with experimental and other theoretical works. This provides a confirmation of the large application field of this method to general correlated two-electron systems.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1434-6079
    Keywords: PACS. 32.80.Pj Optical cooling of atoms; trapping - 33.20.-t Molecular spectra - 34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We report on the formation of translationally cold Cs2 ground state molecules through photoassociation in the 1u attractive molecular state below the 6 s 1/2 +6 p 3/2 dissociation limit. The cold molecules are obtained after spontaneous decay of photoassociated molecules in a MOT and in a dark SPOT. We also used polarized atoms, in the f =3, m f =+3Zeeman ground state. Purely asymptotic and adiabatic calculations including hyperfine interaction and rotation are in excellent agreement with observed structures. As expected, the 1u state is actually a pure long-range state, consisting of paired atoms, uniquely linked by the first terms of the multipole expansion of the electrostatic interaction. A temperature of 20 K has been measured for the molecular cloud.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1434-6079
    Keywords: PACS. 32.80.Pj Optical cooling of atoms; trapping – 34.50.Rk Laser-modified scattering and reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We report the detailed analysis of translationally cold rubidium molecule formation through photoassociation. Cold molecules are formed after spontaneous decay of photoexcited molecules from a laser cooled atomic sample, and are detected by selective mass spectroscopy after two-photon ionization into Rb 2 + ions. A spectroscopic study of the 0 g - (5 S + 5 P 3/2 ) pure long-range state of 87Rb2 is performed by detecting the ion yield as a function of the photoassociation laser frequency; the spectral data are theoretically analyzed within the semiclassical RKR approach. Molecular ionization is resonantly enhanced through either the 2 3 Π g or the 2 3 Σ + g intermediate molecular states. Some vibrational levels of the latter electronic state are observed and assigned here for the first time. Finally, cold molecules formation rates are calculated and compared to the experimentally measured ones, and the vibrational distribution of the formed molecules in the a 3 Σ + u ground triplet state is discussed.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1434-6079
    Keywords: 34.20b ; 31.50+w ; 34.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A two-electron model potential method is proposed to compute diabatic electronic excited states for Na2. The configuration space is first divided into two subspaces corresponding to singly and doubly excited configurations respectively. Next this partition is modified to ensure a correct dissociation limit for the ground state. The matrix element of the electronic Hamiltonian between the two subspaces can be extrapolated along a Rydberg series up to the ionization continuum. The first order M.Q.D.T. treatment of Giusti (1980) is then used to estimate the cross-sections for the reaction Na(3p)+Na(3p)→Na 2 + +e −, considering various symmetries of the intermediate Na2 molecule. A marked selectivity in favour of the3Σ u + symmetry is found and the estimated cross-section σ ∼ 5 Å2 for a collision energy of 0.05 eV is in satisfactory agreement with the experimental results.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 5 (1999), S. 237-242 
    ISSN: 1434-6079
    Keywords: PACS. 31.50.+w Excited states - 33.20.-t Molecular spectra - 33.70.Ca Oscillator and band strengths, lifetimes, transition moments, and Franck-Condon factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Due to competition between ionic and covalent dissociation, the excited potential curves of the alkali dimers display long range structures, leading in some cases to secondary wells. We discuss the possibility of populating the well (with a depth of 1614.8 cm-1, located at R e = 30.5a 0 ) that is present in the Na2 potential curve and propose detection schemes.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 15 (2001), S. 355-363 
    ISSN: 1434-6079
    Keywords: PACS. 32.80.Pj Optical cooling of atoms; trapping – 34.50.Rk Laser-modified scattering and reactions – 33.80.Ps Optical cooling of molecules; trapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We propose a new possibility to form ultracold molecules, via photoassociation of a pair of cold atoms into vibrational levels of the external well of an excited electronic state located at intermediate interatomic distance ( ≈ 20 Bohr radii), and embedded in the dissociation continuum above its dissociation limit. The existence of such a well is demonstrated by conventional free-free absorption spectroscopy at thermal energies. Estimation for cold atom photoassociation and cold molecule formation rates are obtained within a perturbative approach [Drag et al., IEEE J. Quant. Electr. 36, 1378 (2000)], and are found observable for usual conditions of photoassociation experiments.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1434-6079
    Keywords: PACS. 33.80.Eh Autoionization, photoionization, and photodetachment – 33.80.Gj Diffuse spectra; predissociation, photodissociation – 33.80.Ps Optical cooling of molecules; trapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We present the results of absorption measurements in a cesium vapor around 630 K, together with photoionization spectra through a resonance-enhanced two-photon absorption of ultracold cesium dimers created after photoassociation of ultracold cesium atoms. The maximum efficiency of the ultracold molecule ionization is found for wavelengths where absorption at thermal energies is the strongest, in agreement with our theoretical simulations of both processes, involving the so-called Cs2 diffuse bands. This result will be helpful for further optimization of such a direct way of detection of ultracold molecules.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 32 (1994), S. 229-240 
    ISSN: 1434-6079
    Keywords: 34.20.b ; 31.50.+w ; 34.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In a recent paper, we have performed accurate model potential calculations for the adiabatic excited states of the Na2 molecule. In view of dynamical calculations we propose a method to extract doubly excited potential curves, singly excited Rydberg series, and electronic couplings. In contrast to the previous work, the diabatic curves are correctly matching the adiabatic curves at large internuclear distances, and the electronic interactions do vanish in the asymptotic region. The adequacy of scaling laws to extract reduced parameters relevant to MQDT treatment of molecular autoionization is discussed. These parameters are used to calculate cross-sections for the associative ionization reaction at thermal collision energies when fine structure splitting can be neglected. In the framework of a simple model for the treatment of the long range dynamical couplings, we show the strong influence of the initial preparation of the atoms, and of long range population transfers. In contrast to the usual interpretation of experimental data, we predict that at least four doubly excited states may contribute efficiently to the process. Nevertheless, we may reproduce the marked variation of the observed ion signal as a function of the polarization of the exciting light. This work is a step towards a full treatment of the associative ionization between two cold atoms.
    Type of Medium: Electronic Resource
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