Blue laser cooling transitions in Tm I

Abstract

We have studied possible candidates for laser cooling transitions in $^{169}$Tm in the spectral region 410 -- 420 nm. By means of saturation absorption spectroscopy we have measured the hyperfine structure and rates of two nearly closed cycling transitions from the ground state $4\textrm{f}^{13}6\textrm{s}^2(^2\textrm{F}_0)(J_g=7/2)$ to upper states $4\textrm{f}^{12}(^3\textrm{H}_5)5\textrm{d}_{3/2}6\textrm{s}^2(J_e=9/2)$ at 410.6 nm and $4\textrm{f}^{12}(^3\textrm{F}_4)5\textrm{d}_{5/2}6\textrm{s}^2(J_e=9/2)$ at 420.4 nm and evaluated the life times of the excited levels as 15.9(8) ns and 48(6) ns respectively. Decay rates from these levels to neighboring opposite-parity levels are evaluated by means of Hartree-Fock calculations. We conclude, that the strong transition at 410.6 nm has an optical leak rate of less then $2\cdot10^{-5}$ and can be used for efficient laser cooling of $^{169}$Tm from a thermal atomic beam. The hyperfine structure of two other even-parity levels which can be excited from the ground state at 409.5 nm and 418.9 nm is also measured by the same technique. In addition we give a calculated value of $7(2)$ s$^{-1}$ for the rate of magnetic-dipole transition at 1.14 $\mu$m between the fine structure levels $(J_g=7/2)\leftrightarrow(J'_g=5/2)$ of the ground state which can be considered as a candidate for applications in atomic clocks.Comment: 8 pages, 5 figure

Inner-shell magnetic dipole transition in Tm atoms: A candidate for optical lattice clocks

“…These losses may be related to optical or magnetic Feshbach resonances [55]. Thus, the natural linewidth of the clock transition |J = 7/2 → |J = 5/2 is expected to be not broader than 1.4 Hz which is consistent with the previous measurement in 4 He matrix [54] and the theoretical prediction of 1.14 Hz [56]. The natural linewidth of the transition does not limit the performance of the proposed optical clock (see sec.…”

Theoretical study of the spectroscopic properties of mendelevium (Z=101)

“…The results are presented in Table VI. Since the M1 transition between the fine-structure levels in the 4f 13 6s 2 ground state configuration of Tm is considered as a candidate for a clock transition [30], the lifetime of the 4f 13 6s 2 2 F o 5/2 state was calculated in [30] in two different approximations. We calculate it too, starting from solving the RPA equations (8) and using then the formula (9) for transition rates.…”

Precision laser spectroscopy in fundamental studies

“…Due to the same parity, the transition between them with the wavelength of 1.14 mm turns out to be forbidden in the electric dipole approximation, which makes it an interesting candidate for utilization in optical clocks. The magnetic dipole transition has a spectral line width of about 1 Hz [27] and is highly sensitive to a (as a transition probability between fine-structure components varies as $ a 2 Ry). These properties make it an interesting and promising object for studies of the possible a drift [28].…”

“…Highly stable laser sources for the spectroscopy of the 1.14-mm clock transition are being developed there as well. The thulium energy levels structure has been studied [27]; for the first time, laser cooling of thulium was carried out at the wavelength of 410 nm [29], its trapping was demonstrated using a magnetic trap [30], and secondary cooling was brought about using a weak transition at 530.7 nm [31]. The temperature of the cloud with 10 6 atoms reached the level of 25 mK, which allows reloading it into an optical lattice.…”

“…In 2006, we developed a temperature-and vibrationisolated resonator made from a special material Ð ultralow expansion (ULE) glass [38]. Attracting a set of novel approaches [27,39], we decreased the laser frequency instability to the level of thermal noise, which corresponds to a spectral line width of less than 1 Hz. A number of systems were developed at LPI for different wavelengths: 698 nm (clock transition in strontium), 689 nm (secondary cooling transition in strontium), 1140 nm (clock transition in thulium), and 531 nm (secondary cooling transition in thulium), and the quality factors of the resonators reached values of up to 3 Â 10 5 .…”