Cold Potassium-39 Rydberg Atoms Produced from the AC Magneto-Optical Trap

Abstract

Experiments to study the alternating current magneto-optical trap (AC-MOT) of K-39 atoms and then to study the K-39 Rydberg atoms produced in the AC-MOT were carried out. The laser cooling and trapping process was operated using the closed cycle between the (See full text for abstract) ground state and the (See full text for abstract) excited state in the K-39 atom. The AC-MOT experiment allowed the trapping magnetic field to be switched off rapidly within ~20 microseconds. In this experiment, the K-39 atoms were trapped for 600 microseconds and then the trapping magnetic field was switched off for another 600 microseconds. To completely switch off the AC-MOT, an optical chopper was used to block the optical molasses laser beams during the trapping magnetic field off period. This alternately on-off AC-MOT setup produced a cold K-39 trap with a vertical radius of ~1.67 mm and a horizontal radius of ~1.79 mm. The number of trapped atoms in the steady state was (See full text for abstract) atoms corresponding to a trap density of (See full text for abstract). The trap temperature was estimated to be between 146-725 micro-Kelvin. During the AC-MOT off period, the K-39 Rydberg atoms were produced in the cold K-39 trap by a step-wise method. A 770 nm laser beam was used to produce the (See full text for abstract) transition and then a blue laser beam (~454 nm) was used to produce the Rydberg atoms via the (See full text for abstract) transitions. The (See full text for abstract) ions were produced by collisional ionization of the Rydberg atoms and a channel electron multiplier was used to detect these ions. The Rydberg spectra of the 62D-71S states was then obtained. These results suggested for any given pair of the nD state and (See full text for abstract) state, excitation to the nD state was more probable than to the (See full text for abstract) state. The Rydberg spectra of the 120D-131S states were also obtained. In these results, the dipole forbidden (See full text for abstract) transitions were also seen due to the influence of stray external electric fields in the AC-MOT region. An attempt to eliminate these electric fields was made by ensuring the ion extraction pulse was set to 0 V during the Rydberg excitation period. The Rydberg spectra from this experiment showed that the nP state peak heights were reduced, but were not completely eliminated. These results indicated that other fields inside the system were causing these dipole forbidden excitation processes. Better understanding of the K-39 Rydberg atom was achieved from observation of the Rydberg spectra and observations of the influence of the external electric field on the Rydberg atom. This study benefits the understanding of the Rydberg atom in general and is useful for further researches that involve the Rydberg atom, such as an electric field sensor and quantum computing using the Rydberg atom.

Date of Award	1 Aug 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	George King (Supervisor) & Andrew Murray (Supervisor)