The paper reports experimental investigations on 171 Yb ions confined in a radiofrequency Paul trap. Single ions are cooled and optically detected by laser excitation of the cycling F = 1 – F = 0 hyperfine component of the 2 S 1/2 – 2 P 1/2 resonance transition. The metastable 2 D 3/2 ( F = 1) level which is rapidly populated by decay from the 2 P 1/2 level is depleted by a second laser source. The resonance fluorescence signal exhibits dark periods due to a small rate of spontaneous transitions to the 2 D 3/2 ( F = 2) level which is coupled only weakly to the laser-cooling excitation cycle. Prospects for an optical frequency standard based on excitation of the narrow 2 S 1/2 ( F = 0) – 2 D 3/2 ( F = 2) transition of 171 Yb + at a wavelength of 435 nm are discussed.
In order to exploit the capability of a high-Q transition for a frequency standard in the optical domain (729 nm), a stored Ca+ ion cloud in a medium-size ion trap is investigated. Long confinement times are obtained in the presence of helium as a buffer gas in the range 10-6-10-8 mbar and at a pseudopotential well depth of 62 eV. First observations of the electric quadrupole line were achieved by direct excitation of one of the first metastable doublet levels (τ≈1 s). Utilisation of a grating-stabilised diode laser in order to probe both levels when only one level is initially populated allows us to observe almost equal fluorescence intensities of both forbidden lines that show the presence of a strong fine structure mixing which exists in addition to quenching.
We report on a study to determine the efficiency of various buffer gases in quenching the population trapping states of laser-excited ytterbium ions. The ions were confined in an rf-dc hybrid trap, and their
2S1/2${\mathrm{\ensuremath{\leftrightarrows}}}^{2}$
P3/2 transition was excited with 329-nm laser light. Buffer gases used include
H2,
N2,
CO2, Ar, and He at several different pressure regimes. We have identified
N2 to be highly efficient in quenching the population of the trapping states and thus be the most suitable buffer gas to use with ytterbium for the development of a trapped-ion microwave frequency standard.
Long-lived metastable states of
Yb+ ions are used for atomic frequency standards, precision measurements, and quantum information research. The effect of population trapping and transfer in these states must be well understood. We report here the transfer of
Yb+ ions into the long-lived
2F7/2 state by means of collisions between He buffer gas and
Yb+ ions held in a linear Paul trap. Transfer rates were measured as functions of buffer-gas pressure and repump-laser power, and the collisional population transfer rates were extracted. The measured transfer rate coefficients are $8.32(75)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ and $8.65(33)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}\text{ }{\text{cm}}^{3}/\text{s}$ for the collisional processes ${^{2}P}_{1/2}\ensuremath{\rightarrow}{^{2}D}_{5/2}$ and ${^{2}D}_{3/2}\ensuremath{\rightarrow}{^{2}F}_{7/2}$, respectively.
It is known that fluorescence of trapped
Yb+ ions fades with continuous driving of the
2 S1/2${\mathrm{\ensuremath{-}}}^{2}$
P1/2 transition in the presence of buffer gases. This phenomenon has been interpreted as being caused by population trapping in the
2 F7/2 state of
Yb+ . As another cause of the fluorescence disappearance, we found the production of
YbH+ by chemical reaction of
Yb+ in excited states with
H2 gas. We found that the wavelengths of 369.482, 369.202, and 368.947 nm, formerly assigned as wavelengths for deexcitation of
Yb+ in the
2 F7/2 state to the
2 S1/2 ground state, are actually photodissociation lines of
YbH+ . The change of the resonance point of rf resonance absorption signals indicates the production and dissociation of
YbH+ ions. The production of
YbH+ may be a problem in establishing frequency standards using buffer-gas-cooled
Yb+ , owing to difficulty in removing
H2 gas from vacuum systems.
We report on a study to determine the efficiency of various buffer gases in quenching the population trapping states of laser excited ytterbium ions. The ions were confined in an rf/dc hybrid trap, and their /sup 2/S/sub 1/2//spl hArr//sup 2/P/sub 3/2/ transition was excited with 329 nm laser light. Buffer gases used include H/sub 2/, N/sub 2/, CO/sub 2/, Ar, and He at several different pressure regimes. We have identified N/sub 2/ to be highly efficient in quenching the population of the trapping states, and thus be the most suitable buffer gas to use with ytterbium for the development of a trapped ion microwave frequency standard.