We report enhanced sub-Doppler cooling of the bosonic atoms of 39 K facilitated by formation of dark states tuned for the Raman resonance in the Λ−configuration near the D1 transition. Temperature of about 12 µK is achieved in the two stage D2-D1 molasses and spans a very large parameter region where quantum interference persists robustly. We also present results on enhanced radiation heating with sub-natural linewidth (0.07Γ) and signature Fano like profile of a coherently driven 3-level atomic system. The Optical Bloch Equations relevant for the three-level atom in bichromatic light field is solved with the method of continued fractions to show that cooling occurs only for a small velocity class of atoms, emphasizing the need for pre-cooling in D2 molasses stage.
We report the sub-Doppler deep-cooled three-dimensional magneto-optical trap (3D MOT) of the fermionic 40K and bosonic 39K isotopes of potassium loaded by a very compact 2D+ MOT with a novel optical design feature. The set-up is meant for studies on the quantum dynamics of a few fermionic and bosonic atoms in an optical dipole trap near and well within quantum degeneracy. The loading rate and atom numbers achieved in the compact simple set-up are comparable to those in the previous set-ups with more elaborate vacuum design. We attained relatively low temperatures of 34 and 30 µK for 39K and 40K after the sub-Doppler cooling process.
We study the spectroscopy of atoms dressed by a resonant radiofrequency (RF) field inside an inhomogeneous magnetic field and confined in the resulting adiabatic potential. The spectroscopic probe is a second, weak, RF field. The observed line shape is related to the temperature of the trapped cloud. We demonstrate evaporative cooling of the RF-dressed atoms by sweeping the frequency of the second RF field around the Rabi frequency of the dressing field.
We discuss the quality required for the RF source used to trap neutral atoms in RF-dressed potentials. We illustrate this discussion with experimental results obtained on a Bose-Einstein condensation experiment with different RF sources.
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