We demonstrate launching of laser-cooled Yb atoms in a cold atomic fountain. Atoms in a collimated thermal beam are first cooled and captured in a magneto-optic trap (MOT) operating on the strongly-allowed ${^1S}_0 \rightarrow {^1P}_1$ transition at 399~nm (blue line). They are then transferred to a MOT on the weakly-allowed ${^1S}_0 \rightarrow {^3P}_1$ transition at 556~nm (green line). Cold atoms from the green MOT are launched against gravity at a velocity of around 2.5~m/s using a pair of green beams. We trap more than $10^7$ atoms in the blue MOT and transfer up to 70\% into the green MOT. The temperature for the odd isotope, $^{171}$Yb, is $\sim$1~mK in the blue MOT, and reduces by a factor of 40 in the green MOT.Comment: 6 pages, 7 figure

It is generally admitted that in quantum mechanics, the electromagnetic potentials have physical interpretations otherwise absent in classical physics as illustrated by the Aharonov-Bohm effect. In 1984, Berry interpreted this effect as a geometrical phase factor. The same year, Wilczek and Zee generalized the concept of Berry phases to degenerate levels and showed that a non-Abelian gauge field arises in these systems. In sharp contrast with the Abelian case, spatially uniform non-Abelian gauge fields can induce particle noninertial motion. We explore this intriguing phenomenon with a degenerated Fermionic atomic gas subject to a two-dimensional synthetic SU(2) non-Abelian gauge field. We reveal the spin Hall nature of the noninertial dynamic as well as its anisotropy in amplitude and frequency due to the spin texture of the system. We finally draw the similarities and differences of the observed wave packet dynamic and the celebrated Zitterbewegung effect of the relativistic Dirac equation.

We demonstrate launching of laser-cooled Yb atoms in a continuous atomic beam. The continuous cold beam has significant advantages over the more-common pulsed fountain, which was also demonstrated by us recently. The cold beam is formed in the following steps-(i) Atoms from a thermal beam are first Zeeman slowed to a small final velocity, (ii) the slowed atoms are captured in a two-dimensional magneto-optic trap (2D-MOT), and (iii) atoms are launched continuously in the vertical direction using two sets of moving-molasses beams, inclined at ±15 • to the vertical. The cooling transition used is the strongly-allowed 1 S0 → 1 P 1 transition at 399 nm. We capture about 7 × 10 6 atoms in the 2D-MOT, and then launch them with a vertical velocity of 13 m/s at a longitudinal temperature of 125(6) mK.

We report on damage to DNA in an aqueous medium induced by ultrashort pulses of intense laser light of 800 nm wavelength. Focusing of such pulses, using lenses of various focal lengths, induces plasma formation within the aqueous medium. Such plasma can have a spatial extent that is far in excess of the Rayleigh range. In the case of water, the resulting ionization and dissociation gives rise to in situ generation of low-energy electrons and OH-radicals. Interactions of these with plasmid DNA produce nicks in the DNA backbone: single strand breaks (SSBs) are induced as are, at higher laser intensities, double strand breaks (DSBs). Under physiological conditions, the latter are not readily amenable to repair. Systematic quantification of SSBs and DSBs at different values of incident laser energy and under different external focusing conditions reveals that damage occurs in two distinct regimes. Numerical aperture is the experimental handle that delineates the two regimes, permitting simple optical control over the extent of DNA damage.

We report magnetic trapping of Yb in the excited 3 P 2 state. This state, with a lifetime of 15 s, could play an important role in studies ranging from optical clocks and quantum computation to the search for a permanent electric dipole moment. Yb atoms are first cooled and trapped in the ground state in a 399-nm magneto-optic trap. The cold atoms are then pumped into the excited state by driving the 1 S 0 → 3 P 1 → 3 S 1 transition. Atoms in the 3 P 2 state are magnetically trapped in a spherical quadrupole field with an axial gradient of 110 G/cm. We trap up to 10 6 atoms with a lifetime of 1.5 s.