Radiative binding of slowly colliding atoms into a molecule in a laser field

M. Ya. Agre, Л. П. Рапопорт

A. Jacob, C. Müller, Alexander B Voitkiv

It is generally assumed that for ionization processes, which occur in slow atomic collisions, the coupling of the colliding system to the quantum radiation field is irrelevant. Here we show, however, that -- contrary to expectations -- such a coupling can strongly influence ionization of a beam of atomic species A slowly traversing a gas of atomic species B excited by a weak laser field. Moreover, this coupling becomes even more important when the collision velocity increases, getting comparable or exceeding the typical electron orbiting velocities in A and B. Our results imply furthermore that the Breit interaction can, in fact, dominate over the Coulomb interaction at very low energies.

Ye Li

Emanuel F. de Lima

Photoassociation is a possible route for the formation of chemical bonds. In this process, the binding of colliding atoms can be induced by means of a laser field. Photoassociation has been studied in the ultracold regime and also with temperatures well above millikelvins in the thermal energy domain, which is a situation commonly encountered in the laboratory. A photoassociation mechanism can be envisioned based on the use of infrared pulses to drive a transition from free colliding atoms on the electronic ground state to form a molecule directly on that state. This work takes a step in this direction, investigating the laser-pulse-driven formation of heteronuclear diatomic molecules in a thermal gas of atoms including rotational effects. Based on the assumption of full system controllability, the maximum possible photoassociation yield is deduced. The photoassociation probability is calculated as a function of the laser parameters for different temperatures. Additionally, the photoassociation yield induced by subpicosecond pulses of a priori fixed shape is compared to the maximum possible yield.

Bimalendu Deb

In contrast to atomic cooling achieved through laser techniques, molecular cooling generally involves not only cooling translational motion but also vibrational and rotational motion. Cooling molecules directly using the laser cooling method is an extremely difficult or even impossible-seeming task in most cases at present. An alternative approach is to associate two colliding cold atoms to form a molecule that is translationally and rotationally cold. The method by which two cold atoms bind together into a molecule in the presence of external fields is called ‘association spectroscopy,’ which is an inelastic collision process afforded by an external field. There are three kinds of association spectroscopy: (1) photoassociation (PA), (2) magnetoassociation, and (3) magneto-optical association. We briefly discussed PA in the previous chapter. This type of spectroscopy is a result of advancements in the field-assisted collision physics of cold atoms. In this chapter, we provide a description of these three types of association spectroscopy.

André D. Bandrauk