Searcharxiv⌕ Search

arXiv subjects

F. Masnou-Seeuws

Publications and source records attributed to F. Masnou-Seeuws.

4 recordsLinked to original sources
arXiv2008

Application of B-splines to determining eigen-spectrum of Feshbach molecules

The B-spline basis set method is applied to determining the rovibrational eigen-spectrum of diatomic molecules. A particular attention is paid to a challenging numerical task of an accurate and efficient description of the vibrational levels near the dissociation limit (halo-state and Feshbach molecules). Advantages of using B-splines are highlighted by comparing the performance of the method with that of the commonly-used discrete variable representation (DVR) approach. Several model cases, including the Morse potential and realistic potentials with 1/R^3 and 1/R^6 long-range dependence of the internuclear separation are studied. We find that the B-spline method is superior to the DVR approach and it is robust enough to properly describe the Feshbach molecules. The developed numerical method is applied to studying the universal relation of the energy of the last bound state to the scattering length. We numerically illustrate the validity of the quantum-defect-theoretic formulation of such a relation for a 1/R^6 potential.

physics.atom-ph↗
arXiv2007

Grid methods for cold molecules : determination of photoassociation lineshapes and rate constants

A description of photoassociation by CW laser is formulated in the framework of grid methods. The Hamiltonian describing one or several bound states coupled to a multiple of continuum manifolds via a radiative field is written in the energy representation and diagonalized. The generality of the treatment allows to compute accurately and efficiently physical properties such as non-linear high-intensity energy shifts, line shapes, and photoassociation rates both for isolated and non-isolated resonances. Application is given to sodium photoassociation in the experimental conditions of Mc Kenzie {\it et al} [Phys. Rev. Lett. {\bf 88}, 090403 (2002)]. Inverted region for the dependency of the rate vs. the intensity and non-symmetric lineshapes were predicted to occur above the saturation limit. Comparison with the model of Bohn and Julienne [Phys. Rev. A {\bf 60}, 414 (1999)] is discussed.

physics.chem-ph↗
arXiv2004

Photoassociation of cold atoms with chirped laser pulses: time-dependent calculations and analysis of the adiabatic transfer within a two-state model

This theoretical paper presents numerical calculations for photoassociation of ultracold cesium atoms with a chirped laser pulse and detailed analysis of the results. In contrast with earlier work, the initial state is represented by a stationary continuum wavefunction. In the chosen example, it is shown that an important population transfer is achieved to $\approx 15$ vibrational levels in the vicinity of the v=98 bound level in the external well of the $0_g^-(6s+6p_{3/2})$ potential. Such levels lie in the energy range swept by the instantaneous frequency of the pulse, thus defining a ``photoassociation window''. Levels outside this window may be significantly excited during the pulse, but no population remains there after the pulse. Finally, the population transfer to the last vibrational levels of the ground $a^3Σ_u^+$(6s + 6s) is significant, making stable molecules. The results are interpreted in the framework of a two state model as an adiabatic inversion mechanism, efficient only within the photoassociation window. The large value found for the photoassociation rate suggests promising applications. The present chirp has been designed in view of creating a vibrational wavepacket in the excited state which is focussing at the barrier of the double well potential.

physics.atm-clus↗