Blue laser cooling transitions in Tm I

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

Gamma Factory at CERN – novel research tools made of light

We discuss the possibility of creating novel research tools by producing and storing highly relativistic beams of highly ionised atoms in the CERN accelerator complex, and by exciting their atomic degrees of freedom with lasers to produce high-energy photon beams. Intensity of such photon beams would be by several orders of magnitude higher than offered by the presently operating light sources, in the particularly interesting gamma-ray energy domain of 0.1-400 MeV. In this energy range, the high-intensity photon beams can be used to produce secondary beams of polarised electrons, polarised positrons, polarised muons, neutrinos, neutrons and radioactive ions. New research opportunities in a wide domain of fundamental and applied physics can be opened by the Gamma Factory scientific programme based on the above primary and secondary beams.Comment: 12 pages; presented by W. Placzek at the XXV Cracow Epiphany Conference on Advances in Heavy Ion Physics, 8-11 January 2019, Cracow, Polan

Evaluation of excited nl-state distributions of fast exit ions after penetrating through solid foils. Part 2: Determination of the nl-state distribution fractions of exit ions

In Part 1 [T. Miyoshi, K. Noda, Y. Sato, H. Tawara, I.Yu. Tolstikhina, V.P. Shevelko, Nucl. Instr. and Meth. B, this issue] of our two reports, new experimental data on charge-state evolution Fq(D) and equilibrium fractions Click to view the MathML source were presented when 4.3 MeV/u projectile ions with the atomic number Z = 6–26 pass through carbon. Also, in this paper, a ten-charge-state model for equilibrium fractions Click to view the MathML source expressed in terms of the charge-changing cross sections was suggested. In the present work (Part 2), a new method is suggested to determine the nl-distributions Nq(nl) of exit ions with a charge q in the specific nl-states by solving the balance equations with all appropriate effective cross sections as coefficients. The Click to view the MathML source and Nq(nl) values are normalized so that Click to view the MathML source and Click to view the MathML source. The efficiency of the present method suggested is illustrated by example of Ar ions colliding with a carbon foil at projectile energy of E = 6.0 MeV/u. It is found that the exit argon beam comprises about 12% of argon ions in the excited states. This method can be used for evaluation of the excited-ion components in the exit ion beam when the charge equilibrium has been reached. Besides, in this work, extending the method described in [Miyoshi et al., this issue], evaluation of nl-state distributions of exit ions at energies E = 4–20 MeV/u is performed for the case of Ar + C foil collisions, therefore, allowing to observe the nl-state distributions in a wide energy range

Evaluation of excited nl-state distributions of fast exit ions after penetrating through solid foils. Part 1: Charge-state fractions for 4.3 MeV/u projectiles with atomic numbers Z = 6-26 passing through carbon foils

New experimental data on charge-state evolution fractions Fq(D) and equilibrium charge fractions Click to view the MathML source are presented when 4.3 MeV/u projectile ions with an atomic number Z = 6–26 passed through carbon foils with thickness of D = 10–350 μg/cm2. These data are compared with the data at 6.0 MeV/u previously reported, and the difference is explained in terms of the energy dependence of the charge-changing cross sections in solid carbon. Using the equations relating the equilibrium fractions Click to view the MathML source with the collision cross sections describing interaction of projectiles with the target atoms, the nl state distributions of exit ions are predicted where n and l are the principal and orbital quantum numbers, respectively. A fitting procedure of getting information about these distributions is described. The influence and importance of the so-called target-density (gas–solid) effects on the collision cross sections for solid targets are also discussed. Using the fitting procedure described in this paper (Part 1), one can obtain information on nl state distributions, which survived after collisions of the projectiles with the target atoms. In the coming second part (Part 2) of our two reports, it will be shown how to estimate the absolute number of exit ions in these nl states