Isotopic structure of the 4f 14 6s 2 (6 1 S 0 )- 4f 14 6s7s(7 1 S 0 ) transition in the Yb i atom

A Ya Kraftmakher

Jian Li, William Arie van Wijngaarden

K. Chebakov, N. Kolachevsky, Alexey V. Akimov +4 more

Full text: It has been shown recently that Yb and Er atoms from the lanthanides group can be efficiently laser-cooled using strong transitions near 400 nm. Degenerate Fermi gases of ytterbium have been also recently demonstrated using laser-cooling based technic. Our goal was to investigate the possibility of laser cooling of Tm atom. Among other lanthanides, thulium possesses relatively simple level structure.Moreover, it has only one stable isotope {sup 169}Tm with a nuclear spin of I = 1/2 which makes possible to use schemes for sub-Doppler cooling. Laser-cooled thulium is a favorable candidate for optical clocks applications, since the forbidden transition between the fine structure sublevels (J{sub g} 5=2) - (J'{sub g} = 7/2) of the ground state 4f{sup 13}6s{sup 2} ({lambda} = 1.14 micron) has a spectral width of approximately 1 Hz. The collisional shift of such kind of transitions in lanthanides is suppressed because of the outer closed 6s{sup 2} shell, which allows for precision spectroscopy in a dense atomic cloud. We studied two candidates for cooling transitions from the ground state 4f{sup 13}6s{sup 2} (J{sub g} 7/2) to the states 4f{sup 12}({sup 3}H{sub 5})5d{sub 3/2}6s{sup 2} (J{sub e} = 9/2) at 410.6 nm and 4f{sup 12}({sup 3}F{sub 4})5d{sub 5/2}6s{sup 2} (J{sub e} = 9/2) at 420.4 nm. By means of saturation absorption spectroscopy, we measured the hyperfine structure and rates of these transitions. We evaluated the life times of appropriate excited levels as 15.9(8) ns and 48(6) ns, respectively. Decay rates from these levels to neighboring opposite-parity levels were evaluated by means of Hartree-Fock calculations. The fraction of atoms which do not return to the ground state is about 10{sup -5} and 5 {center_dot} 10{sup -4} for the 410.6 nm and 420.4 nm transitions respectively. We conclude that the strong transition at 410.6 nm with relative slow leakage rate can be used for the efficient cooling of Tm I. We also measured hyperfine structure of two nearby transitions from the ground state to the states 4f{sup 13}({sup 2}F{sub 7/2})6s6p({sup 1}P{sub 1}) (J{sub e} 5/2) at 409.4 nm and 4f{sup 12}({sup 3}F{sub 4})5d{sub 5/2}6s{sup 2} (J{sub e} = 7/2) at 418.9 nm, which can be used for {lambda}-type excitation of {lambda} = 1.14 {mu}m transition. (author)

Masayuki Kawamura, Wei-Guo Jin, Nichika Kobayashi +2 more

L. Barbier, R.-J. Champeau

High Rydberg levels of ytterbium were studied in a beam of metastable atoms. Levels of the series 4f$^{14}$ 6$sn$d were populated from the metastable 4f$^{14}$ 6s 6p $^3$P$_o$ level by means of the U.V. light of a frequency-doubled single-mode dye laser and detected using the field ionization technique. The critical ionization fields $F_c$ of the levels 4f$^{14}$ 6$sn$d $^3$D$_1$ (24 ≤ n ≤ 57) were measured and found to obey the saddle point law ($F_c$ = (16 $n^{*4}$)$^{-1}$). The hyperfine structures of the odd isotopes were investigated. They are very peculiar due to the fact that the hyperfine interaction is of the same order of magnitude as (or even for the highest $n$ values, much more important than) the spin-orbit and electrostatic interactions. A theoretical account of the observed structures using the Slater-Condon parametric method is given. The relative influence of the excited ($n$d) and of the non-excited (6s) optical electron could thus be studied. Furthermore the influence of a valence level perturbing only the odd isotopes components for $n$ = 26 was demonstrated.

Paul S. Julienne, R. Ciuryło, Masaaki Kitagawa +3 more