Laboratory of Atomic Interactions
The laboratory of atomic interactions (LIA in Portuguese) is dedicated to the study of atomic interaction in cold trapped atom samples. In order to achieve such goal, we apply laser cooling and trapping techniques on potassium and rubidium atoms. There are two experimental setups, one devoted to Rydberg atoms and another to heteronuclear atomic samples.
Cold Rydberg Atoms: In the past, we have investigated population transfer processes involving cold Rydberg atoms in a Rb magneto-optical trap. Such processes can interpret considering nonadiabatic multichannel decay of Rydberg atom diatomic quasi-molecules on long range potentials. The calculation of such potentials includes dipole-dipole, dipole-quadrupole and quadrupole-quadrupole interactions as well as the dc Stark effect and atomic fine structure. The same calculations suggest that quadrupole-quadrupole interactions may be important at short range.
In order to test it, we built a new optical dipole trap setup. In this setup, Rb atoms, from a standard magneto optical trap, are loaded into a CO2 optical dipole trap. This allows us to obtain a sample with a peak density of about 1012 atoms/cm3 at a temperature of 30 ľK. Using a two resonant photons (at 780 and 480 nm), either nS or nD Rydberg states can be excited. In the sequence, we can observe population transfer to nearby states due to interactions. We hope this setup will allow us to test the short range part of the potentials.
Cold Heteronuclear Sample: Our laboratory was the first to observe cold heteronuclear ground state molecules using a two species magneto optical trap with K and Rb atoms. The molecules were formed in a high vibrational level due to photoassociation by the MOT laser beams. Due to the low atomic density we were unable to perform more experiments.
In order to overcome such limitation, we have built a crossed optical dipole trap for K and Rb. Both species are first slowed in an atomic beam then captured and cooled in a dual species MOT. Then the atoms are transferred to a crossed optical dipole trap formed by a 1070 nm broadband laser. In fact, this was the first time that K atoms were loaded into an optical dipole trap directly from a MOT.
Using such a high density sample, recently, we were able to observe photoassociation due to the 1070 nm laser in Rb. There are evidences that the same process also happens for K and Rb, forming KRb molecules. Now, we are investigating the role of the 1070 nm on the formation and trapping of cold homonuclear and heteronuclear molecules. The laboratory counts with: i) Several diode laser and amplifier systems at 480, 766 and 780 nm; ii) Two high power laser (CO2 and 1070 nm) for the dipole traps; iii) Pulsed dye laser, iv) Several eletronic equipments.
Our laboratory also applies spectroscopy technique in agriculture problems. We are interested on early disease detection and post harvest non invasive spectroscopy imaging techniques. The present research involves application on orange leaves, grapes and papaya.