Biomedical subjects

O Dulieu

Publications and source records attributed to O Dulieu.

10 recordsLinked to original sources

PubMed2005

Calculation of accurate permanent dipole moments of the lowest 1,3Sigma+ states of heteronuclear alkali dimers using extended basis sets.

Obtaining ultracold samples of dipolar molecules is a current challenge which requires an accurate knowledge of their electronic properties to guide the ongoing experiments. In this paper, we systematically investigate the ground state and the lowest triplet state of mixed alkali dimers (involving Li, Na, K, Rb, Cs) using a standard quantum chemistry approach based on pseudopotentials for atomic core representation, Gaussian basis sets, and effective terms for core polarization effects. We emphasize on the convergence of the results for permanent dipole moments regarding the size of the Gaussian basis set, and we discuss their predicted accuracy by comparing to other theoretical calculations or available experimental values. We also revisit the difficulty to compare computed potential curves among published papers, due to the differences in the modelization of core-core interaction.

Journal Article↗

PubMed2004

Mapped grid methods for long-range molecules and cold collisions.

The paper discusses ways of improving the accuracy of numerical calculations for vibrational levels of diatomic molecules close to the dissociation limit or for ultracold collisions, in the framework of a grid representation. In order to avoid the implementation of very large grids, Kokoouline et al. [J. Chem. Phys. 110, 9865 (1999)] have proposed a mapping procedure through introduction of an adaptive coordinate x subjected to the variation of the local de Broglie wavelength as a function of the internuclear distance R. Some unphysical levels ("ghosts") then appear in the vibrational series computed via a mapped Fourier grid representation. In the present work the choice of the basis set is reexamined, and two alternative expansions are discussed: Sine functions and Hardy functions. It is shown that use of a basis set with fixed nodes at both grid ends is efficient to eliminate "ghost" solutions. It is further shown that the Hamiltonian matrix in the sine basis can be calculated very accurately by using an auxiliary basis of cosine functions, overcoming the problems arising from numerical calculation of the Jacobian J(x) of the R-->x coordinate transformation.

Journal Article↗

PubMed2001

Resonant coupling in the formation of ultracold ground state molecules via photoassociation.

We demonstrate the existence of a new mechanism for the formation of ultracold molecules via photoassociation of cold cesium atoms. The experimental results, interpreted with numerical calculations, suggest that a resonant coupling between vibrational levels of the 0+u (6s+6p1/2) and (6s+6p3/2) states enables formation of ultracold molecules in vibrational levels of the ground state well below the 6s+6s dissociation limit. Such a scheme should be observable with many other electronic states and atomic species.

Journal Article↗

PubMed1999

Photoassociative Spectroscopy and Formation of Cold Molecules in Cold Cesium Vapor: Trap-Loss Spectrum versus Ion Spectrum.

We report on the experimental spectra of all the optically accessible long-range attractive molecular states of the Cs2 dimer below the 6s2S1/2 + 6p2P3/2 dissociation limit by molecular photoassociation of cold Cs atoms. The spectra are obtained by the usual trap-loss method as well as by pulsed-laser photoionization of Cs2 molecules into Cs+2 ions. The two spectra present markedly different features. While the 1g, 0(+)u, and 0(-)g vibrational progressions are present in the trap-loss spectrum, the Cs+2 ion spectrum presents only the 0(-)g and 1u vibrational progressions. Those states (0(-)g and 1u) lead to the formation of the translationally cold Cs2 ground state molecules at temperatures in the 100 µK range, to our knowledge the lowest molecular temperature reported up until now. The C3 asymptotic coefficients for the 0(+)u and 1g states are determined through a fit of the experimental energy levels. Copyright 1999 Academic Press.

Journal Article↗

PubMed1998

Spectroscopy and Lifetimes of the 1(2)Piu State of Na+ 2: A New Comparison between Theory and Experiment.

A detailed theoretical study of the spectroscopy of the 1(2)Piu state of Na+ 2 is presented, including the determination of Dunham coefficients from recent effective potential calculations of the Na+ 2 molecular potential curves. We emphasize the discrepancies existing among several experiments and among several theoretical models available in the literature. The radiative lifetime of the rovibrational levels of the 1(2)Piu state are also computed and are found in agreement within 20% with experiment. Copyright 1998 Academic Press.

Journal Article↗

PubMed1996