Results from measurement of the energy levels of ultra-cold Rydberg states of 39 K in an AC-Magneto-Optical Trap are presented. Rydberg atoms are produced by stepwise excitation from the laser-excited 4 2 P 1 / 2 states using a tunable blue dye laser. Energy level data for principal quantum numbers n = 18 up to n = 199 are reported. For n = 18 to n = 46 , the measured levels are in good agreement with the available data from the National Institute of Standards and Technology (NIST) list of atomic spectral lines. New values for the parameters in the Rydberg-Ritz formula were then calculated from a fit to the measured energy level data. Atomic transition energies for n = 47 to n = 199 are also reported for the first time. Shifts in the levels for excitation to both the 2 S 1 / 2 and 2 D 3 / 2 states at principal quantum number n > 100 are found when compared to calculations derived from the revised Rydberg-Ritz formula. These deviations are due to the greater probability of overlap between the wavefunctions of the excited atoms in the ensemble, resulting in strong interaction between the Rydberg atoms which are in close proximity. For n > 167, the D-state energies were unresolved.
Results from measurement of the energy levels of ultra-cold Rydberg states of 39 K in an AC-Magneto-Optical Trap are presented. Rydberg atoms are produced by stepwise excitation from the laser-excited 4 2 P 1 / 2 states using a tunable blue dye laser. Energy level data for principal quantum numbers n = 18 up to n = 199 are reported. For n = 18 to n = 46 , the measured levels are in good agreement with the available data from the National Institute of Standards and Technology (NIST) list of atomic spectral lines. New values for the parameters in the Rydberg-Ritz formula were then calculated from a fit to the measured energy level data. Atomic transition energies for n = 47 to n = 199 are also reported for the first time. Shifts in the levels for excitation to both the 2 S 1 / 2 and 2 D 3 / 2 states at principal quantum number n > 100 are found when compared to calculations derived from the revised Rydberg-Ritz formula. These deviations are due to the greater probability of overlap between the wavefunctions of the excited atoms in the ensemble, resulting in strong interaction between the Rydberg atoms which are in close proximity. For n > 167, the D-state energies were unresolved.
ABSTRACTCandidate?s Names: John AgomuoDegree Title: PhDThesis Title: Excitation And Photoionization Of Laser-Cooled Atoms In The AC Driven Magneto-Optical Trap (AC-MOT), Using Resonant And Non-Resonant Radiation.Date: 19/12/2014Results of experiments involving the manipulation of atoms using laser radiation are presented. A high-density trap of potassium atoms was created using an AC-driven magneto-optical trap (AC-MOT), loaded from a Zeeman-slowed atomic beam. The AC-MOT was operated in a pulsed mode, with a trapping laser that was detuned by -4?, where ? is the natural line-width of the trapping transition. Under these conditions, the AC-MOT trapped an average of 3.63�0.02�?10?^8 atoms, which were cooled to a mean temperature of 275?K�33?K.Using the AC-MOT, the absolute photoionization cross-section of cold potassium atoms was determined using ionizing laser radiation at 450.4 nm obtained from a high-power diode laser. The measured photoionization cross-section from the 42P3/2 excited state was obtained by measuring the loss rate and the lifetime of the AC-MOT during the loading and decay processes. Using these methods, the cross section was determined to be 1.49�0.13 Mb, and 2.38�0.18 Mb respectively. Precise energy levels of high-n Rydberg states of potassium have also been measured using stepwise-excitation of the trapped atoms, with the intermediate state being the 42P1/2 state that was excited by resonant laser radiation at 389,286,368.12 MHz. Excitation from the 42P1/2 state to the n^2 S_(1/2) states was carried out using blue radiation from a dye laser, for transitions to Rydberg states with principal quantum numbers ranging from n = 18 to ~200. For excitation to the n^2 D_(3/2) states, transitions up to Rydberg states with n ranging from 18 to 167 were studied. Due to the strong interaction between Rydberg atoms, the measured energy levels deviated from their predicted theoretical values at high principal quantum numbers (n?130 for the S-states, and n?100 for the D-states). For principal quantum numbers greater than these values, the spectral lines were found to both broaden and shift in energy, and new features in the Rydberg spectra were observed. These new features have been attributed to the dipole-forbidden n2P1/2 and n2P3/2 states, which cannot be excited directly by the laser. These states must hence be excited due to interplay between the highly excited Rydberg atoms that is occurring due to their large effective size and close proximity in the AC-MOT.
We demonstrate the single-photon Rydberg excitation of cesium atoms in a magneto-optical trap (MOT). We excite atoms directly from 6S1/2ground state to nP3/2(n = 70-100) Rydberg state with a narrow-linewidth 319-nm ultra-violet laser. The detection of Rydberg states is performed by monitoring the reduction of fluorescence signal of the MOT as partial population on 6S1/2(F = 4) ground state are transferred to Rydberg state. We clearly observe Autler-Townes doublet in the trap-loss spectra due to the cooling lights. Utilizing the large electric polarizibility of Rydberg atoms, we observe Stark splitting in the Autler-Townes doublet induced by background DC electric fields. We investigate the dependence of Stark shift on electric fields by theoretical analysis, and then infer the DC electric field from the measured Stark splitting. We find that there is a 44.8(4) mV/cm DC electric field in the vicinity of the cold ensemble. It indicates that high-lying Rydberg atoms can be used as sensors for DC electric fields.
Autler-Townes (A-T) splitting, known as an AC Stark effect, shows a change of an absorption/emission spectral line of a probe beam when an oscillating field is tuned in resonance with the atomic or molecular transition. The A-T splitting is observed in different three-level atoms and widely investigated in a vapor cell and in a magneto-optical trap (MOT). The A-T splitting plays an important role in the atom-based microwave electric-field measurements where a cascade three-level system involving Rydberg state is adopted. In this work, an A-T splitting is observed in an ultracold cesium Rydberg gas, which is cooled down to about 100 pK and center density is about 1010 cm-3 in a conventional MOT by using the laser cooling technology. We present the A-T spectrum in a ladder three-level atomic system involving a 34D5/2 Rydberg state. The cesium ground state (6S1/2), excited state (6P3/2) and Rydberg state (34D5/2) constitute a Rydberg three-level system. A coupling laser, locked to the Rydberg transition by using a Rydberg electromagnetically induced transparency signal that is obtained from a cesium room-temperature vapor cell, couples 6P3/2 (F'=5) 34D5/2 Rydberg transition. A weak probe laser, stabilized to a ground-state transition by using a polarization spectroscopy, is swept, covering the transition 6S1/2 (F=4) 6P3/2 (F'=5) with a double-passed acousto-optic modulator. The probe and coupling lasers are counter-propagated through the MOT center. The power of probe light is 200 pW, corresponding Rabi frequency p=21.05 MHz. During the experiment, 50 s after turning off the trapping laser, both the coupling and probe beams are switched on and last 100 s. The A-T spectrum as a function of the probe detuning is detected with a single-photon counter module detector. We use Gaussian multiple peak fitting to obtain the positions of the A-T peaks and the A-T splitting. The measured A-T splitting is proportional to the Rabi frequency of the coupling light. We numerically solve the density matrix equations to obtain the A-T spectrum, and the calculations reproduce A-T spectra well. The measured A-T splitting shows good agreement with the theoretical calculation for Rabi frequency of the coupling light c29 MHz. The A-T splitting is less than the calculation for the case of c29 MHz, the deviation is mainly attributed to the increased dephasing rate induced by the strong interaction between Rydberg atoms, whose number increases with the coupling laser Rabi frequency. In this work, the adopted method for the cascade three-level system involving Rydberg state is also suitable for -and V-type cases.
We created an ultracold plasma via the spontaneous ionization of cold dense Rydberg atoms of 87Rb in a magneto-optical trap (MOT), and measured the nS1/2 (n = 50–80), nP1/2 (n = 16–23), nP3/2 (n = 16–98), and nD5/2 (n = 49–96) Rydberg levels by detecting the electrons in the ultracold plasma. By fitting the energy levels of Rydberg states, the first ionization potential of 33690.950(11) cm−1 and the quantum defects of S, P, and D orbitals were obtained. The absolute transition energies of nS1/2 (n = 66–80), nP1/2 (n = 16–23), nP3/2 (n = 16–98), and nD5/2 (n = 58–96) states of 87Rb, as well as the quantum defects for p1/2 and p3/2 series, are given for the first time.
Our goal is the preparation and study of ultra- cold plasma and Rydberg matter. We assembled an ex- perimental setup for laser cooling of lithium atoms in a magneto-optical trap (MOT). Trapping of 7 Li atoms in a MOT is demonstrated for a wide range of cooling laser detunings. The number density of 7 Li atoms at different ground-state sublevels is measured by using a probe tun- able laser. The temperature of the trapped atoms is esti- mated. Obtained information is important for the prepara- tion of ultra-cold plasma and highly-excited atoms. duction of recombination in such systems. Our theoreti- cal works show the appearance of short and long-range order (7) and a large reduction of the recombination rate (a few orders of magnitude) in the ultra-cold mixture of Rydberg atoms and plasma in the presence of a strong magnetic field (8-11). The ability to control the decay and crystallization processes in an ensemble of Rydberg atoms could find an application in quantum storage and quan- tum computers. The suggested experiments can model the behavior of the plasma recombination in experiments on creating anti-hydrogen (12-14), and help to increase the number of ground state anti-hydrogen atoms in a strong magnetic field. It is noteworthy that lithium is an element which is very close to hydrogen.