Blue laser cooling transitions in TmI

We have studied possible candidates for laser cooling transitions in Tm-169 in the spectral region of 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 f(13)6s(2)(F-2(0))(J(g) = 7/2) to upper states 4f(12)(H-3(5)) 5d(3)/(2)6s(2)(J(e) = 9/2) at 410.6 nm and 4f(12)(F-3(4)) 5d(5)/(2)6s(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 x 10(-5) and can be used for efficient laser cooling of 169Tm 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 magneticdipole transition at 1.14 mu m between the fine structure levels (Jg = 7/2) <-> (J'(g) = 5/2) of the ground state which can be considered as a candidate for applications in atomic clocks.