A complete set of spectroscopic data is indispensable when using Rydberg states of trapped ions for quantum information processing. We carried out Rydberg series spectroscopy for
nS1/2 states with $38\ensuremath{\le}n\ensuremath{\le}65$ and for
nD5/2 states with $37\ensuremath{\le}n\ensuremath{\le}50$ on a single trapped
40Ca+ ion. We determined the ionization energy of 2 870 575.582(15) GHz, 60 times more accurately as compared to the accepted value and contradicting it by 7.5 standard deviations. We confirm quantum defect values of ${\ensuremath{\delta}}_{{S}_{1/2}}=1.802\text{ }995(5)$ and ${\ensuremath{\delta}}_{{D}_{5/2}}=0.626\text{ }888(9)$ for
nS1/2 and
nD5/2 states, respectively, which allow for unambiguous addressing of Rydberg levels of
Ca+ ions. Our measurements confirm Rydberg ion scaling properties, e.g., for blackbody induced ionization, linewidths and excitation strengths.
We investigate the spectra of the electric quadrupole 4 2 S 1/2 →3 2 D 5/2 transitions in a single 40 Ca + ion confined in a home-built linear trap. We probe the transitions with an ultra-narrow bandwidth laser at 729 nm. In a weak magnetic field, the quadrupole transition splits into ten components with the maximal line strength proportional to their squared Clebsch—Gordan factors. In a magnetic field of the order of Gauss, the observed equidistant sideband reflects the Zeeman substructure modulated by the quantized oscillation due to the secular motion in the trap. The temperature of the trapped ion can be determined by the envelope of the sideband spectrum. We also demonstrate the Rabi oscillation in a carrier transition after the ion has been Doppler cooled, which can be fitted by the model with the thermal state of motion.
We present precise measurements of the quantum defects of cesium
nFJ Rydberg levels. We employ high-precision microwave spectroscopy of $(n+2){D}_{5/2}\ensuremath{\rightarrow}n{F}_{5/2,7/2}$ transitions for
n=45 to 50 in a cold-atom setup. Cold cesium
(n+2)D5/2 atoms, prepared via two-photon laser excitation, are probed by scanning weak microwave fields interacting with the atoms across the
nF5/2,7/2 resonances. Transition spectra are acquired using state-selective electric-field ionization and time-gated ion detection. Transition-frequency intervals are obtained by Lorentzian fits to the measured spectral lines, which have linewidths ranging between 70 and 190 kHz, corresponding to about one to three times the Fourier limit. A comprehensive analysis of relevant line-shift uncertainties and line-broadening effects is conducted. We find quantum defect parameters ${\ensuremath{\delta}}_{0}({F}_{5/2})=0.033\phantom{\rule{0.16em}{0ex}}415\phantom{\rule{0.16em}{0ex}}37(70)$ and ${\ensuremath{\delta}}_{2}({F}_{5/2})=\ensuremath{-}0.2014(16)$, as well as ${\ensuremath{\delta}}_{0}({F}_{7/2})=0.033\phantom{\rule{0.16em}{0ex}}564\phantom{\rule{0.16em}{0ex}}6(13)$ and ${\ensuremath{\delta}}_{2}({F}_{7/2})=\ensuremath{-}0.2052(29)$, for
J=5/2 and
7/2, respectively. Fine-structure parameters
AFS and
BFS for Cs
nFJ are also obtained. Results are discussed in context with previous works, and the significance of the results is discussed.
A single
40Ca+ ion is confined in a linear Paul trap and Doppler-cooled on the
S1/2 to
P1/2 dipole transition. Then the narrow quadrupole
S1/2 to
D5/2 transition at 729 nm is probed. The observed spectrum is interpreted in terms of the Zeeman substructure superimposed with oscillation sidebands due to the harmonic motion in the trap. The height of the motional sidebands provides a sensitive method to determine the ion's temperature and thus allows us to test sub-Doppler laser cooling schemes needed for quantum state preparation and quantum computation. We also observe the dynamics induced by Rabi oscillations on a carrier transition and interpret it in terms of the thermal state which is reached after Doppler cooling.
We present absolute-frequency measurements in ultracold
39K samples of the transitions from the
4s1/2 ground state to
np1/2 and
np3/2 Rydberg states. A global nonlinear regression of the
np1/2 and
np3/2 term values yields an improved wave number of 35009.8139710(22)${}_{\mathrm{sys}}{(3)}_{\mathrm{stat}}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ for the first ionization threshold of
39K and the quantum defects of the
np1/2 and
np3/2 series. In addition, we report the frequencies of selected one-photon transitions ${n}^{\ensuremath{'}}{s}_{1/2}\ensuremath{\leftarrow}n{p}_{3/2}, {n}^{\ensuremath{'}}{d}_{j}\ensuremath{\leftarrow}n{p}_{3/2}, {n}^{\ensuremath{'}}{f}_{{j}^{\ensuremath{'}}}\ensuremath{\leftarrow}n{d}_{j}$, and ${n}^{\ensuremath{'}}{g}_{{j}^{\ensuremath{'}}}\ensuremath{\leftarrow}n{f}_{j}$ and two-photon transitions $n{f}_{{j}^{\ensuremath{'}}}\ensuremath{\leftarrow}n{p}_{j}$ determined by millimeter-wave spectroscopy, where
j is the total angular-momentum quantum number. By combining the results from the laser and millimeter-wave spectroscopic experiments, we obtain improved values for the quantum defects of the
s1/2,d3/2,d5/2,fj, and
gj states. For the
dj series, the inverted fine structure was confirmed for $n\ensuremath{\ge}32$. The fine-structure splitting of the
f series is less than 100 kHz at
n=31, significantly smaller than the hydrogenic splitting, and the fine structure of the
g series is regular for $n\ensuremath{\ge}30$, with a fine-structure splitting compatible with the hydrogenic prediction. From the measured quantum defects of the
f and
g series we derive an estimate for the static dipole ${\ensuremath{\alpha}}_{\mathrm{d}}$ and quadrupole ${\ensuremath{\alpha}}_{\mathrm{q}}$ polarizabilities of the
K+ ion core. Additionally, the hyperfine splitting of the
4s1/2 ground state of
39K was determined to be 461.719700(5) MHz using radio-frequency spectroscopy and Ramsey-type interferometry.
A beam of gold atoms was produced by heating the gold-containing material by an electro-thermal method. Two UV laser beams then irradiated the atomic beam perpendicularly, which excited the Au atoms to very high Rydberg states from their ground states (6S1/2). A high voltage pulsed electric field was then applied to the interaction region approximately 200 ns after the laser pulse, ionising the Au atoms in Rydberg states. By scanning the wavelength of the laser over a certain range, the positions of 38 energy levels of Au atoms in the n 2D3/2 (n=18-38) and n 2S1/2 (n=21-34, 36-38) series have been measured. The ionisation limits of the n 2D3/2 and n 2S1/2 series were determined by parametric fitting to be Ed=74 409.8 (3) cm-1 and Es=74 410.0 (2) cm-1, respectively. The quantum defects of all these levels were also calculated. This measurement is the first for Au in the energy range and channels mentioned above.