High-resolution Spectroscopy Of Strontium Triplet Rydberg Series In An Ultracold Gas

This thesis describes in details an experimental apparatus which is developed to produce an ultracold gas of strontium Rydberg atoms.Strontium atoms are cooled down by a two-dimensional magneto-optical trap followed by a succession of two three-dimensional magneto-optical traps,down to a temperature of 1.3 ?K and at a peak den-sity of 2 x 1010 atoms · cm-3.A laser system at 461 nm has been developed to produce and distribute laser light for the laser cooling scheme.A frequency stabilization based on a wavelength meter has been implemented to provide a convenient way to stabilize lasers to atomic resonances.The atoms are excited to the triplet Rydberg states via the 5s5p3P1 state where the light for the upper transition is generated by a laser system based on a frequency doubled dye laser at 319 nm.The laser system provides UV light with a linewidth of 60 kHz over 100 ms and a long-term center frequency stability better than the natural linewidth of the Rydberg lines.The experimental apparatus is utilized to perform the spectroscopy of the 5s,ns 3S1,5sn.d 3D1 and 5snd 3D2 Rydberg series of strontium.The energies of the Rydberg states in the range n = 12...50 are measured by atom-loss spectroscopy using a high accu-racy wavelength meter,which is extensively characterized,while the absolute frequency calibration is ensured by performing Doppler-free absorption spectroscopy of iodine molecules.The atom-loss spectra are interpreted using a simple model and combined with a frequency uncertainty budget,yielding an absolute frequency uncertainty on the Rydberg state energies of 10 MHz.An estimation of the quantum defect is extracted as well as a new value for the first ionization limit.The setup presented in this thesis is a basis for the implementation of future quan-tum simulation experiments.The experimental Rydberg state energies determined in this thesis are an important resource which can be used to compute the properties of the Rydberg atoms,necessary to design and interpret such quantum simulation experiments.