Light interaction with atoms and molecules

V. I. Romanenko, Ye. G. Udovitskaya, A. V. Romanenko +1 more

We discuss a possible one-dimensional trapping and cooling of atoms and molecules due to their nonresonant interaction with counterpropagating light pulse trains. The counterpropagating pulses form a one-dimensional trap for atoms and molecules and a properly chosen carrier frequency detuning from the transition frequency of the atoms or molecules keeps the temperature of the atomic or molecular ensemble close to the Doppler cooling limit. The calculation by the Monte Carlo wave-function method is carried out for the two-level and three-level schemes of the atom's and the molecule's interaction with the field, respectively. The models discussed are applicable to atoms and molecules with almost diagonal Frank-Condon factor arrays. Illustrative calculations are carried out for ensemble-averaged characteristics for sodium atoms and SrF molecules in the trap. The potential for the nanoparticle light pulses's trap formed by counterpropagating light pulse trains is also discussed.

Crispin W. Gardiner, P. Zoller

Pradip Kumar Mondal, Bimalendu Deb, Sonjoy Majumder

The exchange of orbital angular momentum between a Laguerre-Gaussian beam of light and the center-of-mass motion of an atom or molecule is well known. We show that the orbital angular momentum of light can also be transferred to the internal electronic or rotational motion of an atom or a molecule provided the internal and center-of-mass motions are coupled. However, this transfer does not happen directly to the internal motion, but via center-of-mass motion. If atoms or molecules are cooled down to the recoil limit, then an exchange of angular momentum between the quantized center-of-mass motion and the internal motion is possible during the interaction of cold atoms or molecules with the Laguerre-Gaussian beam. The orientation of the exchanged angular momentum is determined by the sign of the winding number of the Laguerre-Gaussian beam. We present selective results of numerical calculations for the quadrupole transition rates in the interaction of the Laguerre-Gaussian beam with an atomic Bose-Einstein condensate to illustrate the underlying mechanism of light orbital angular momentum transfer. We discuss how the alignment of diatomic molecules will facilitate exploration of the effects of light orbital angular momentum on the electronic motion of molecules.

Crispin W. Gardiner

Jonathan D. Pritchard

Yan Qin, Rong Chang, Sheng-Chang Li

We investigate the quantum many-body dynamics of ultracold atom−molecule conversion using a Floquet spin-boson model, where the periodic energy detuning between molecules and atomic pairs is utilized to explore various dynamical regimes. We find that the upper bound of the adiabatic driving frequency increases continuously with the strength of molecule−molecule interactions, indicating that many-body interactions are beneficial in meeting the requirement of the adiabatic condition, thereby facilitating the realization of adiabatic atom−molecule conversion. This enhancement of the fulfillment of the adiabatic condition is further evidenced by the stabilization of periodic oscillations in the mean molecule number over time, protected by these interactions, even when the frequency lies within the localized regime. Interestingly, in the diffusive regime, while the many-body interaction has little effect on the dynamical equilibrium of atom−molecule conversion, it significantly expands the diffusive regime. In the high-frequency limit, many-body interactions are found to completely suppress atom−molecule conversion. Our results shed light on how molecule−molecule interactions influence the boundaries between different dynamical regimes.