PDF《Cold beam of isotopically pure Yb》

arXiv:1310.

7733v2 [physics.atom-ph]

25 Feb

2015 Cold beam of isotopically pure Yb atoms by de?ection using 1D-optical molasses Ketan D. Rathod, P. K. Singh, and Vasant Natarajan Department of Physics, Indian Institute of Science, Bangalore

560 012, India We demonstrate generation of an isotopically pure beam of laser-cooled Yb atoms by de?ection using 1D-optical molasses. Atoms in a collimated thermal beam are ?rst slowed using a Zeeman Slower. They are then subjected to a pair of molasses beams inclined at 45? with respect to the slowed atomic beam. The slowed atoms are de?ected and probed at a distance of

160 mm. We demonstrate selective de?ection of the bosonic isotope

174 Yb, and the fermionic isotope

171 Yb. Using a transient measurement after the molasses beams are turned on, we ?nd a longitudinal temperature of

41 mK. PACS numbers: 37.10.De, 42.50.Wk, 32.10.Dk I. INTRODUCTION Cold atoms [1], with their long measurement times, promise to revolutionize the ?eld of precision measure- ments. In this respect, laser-cooled Yb constitutes a use- ful species because its spin-zero ground state obviates the need for a second repumping laser, as is required for laser cooling of the more common spin-half alkali-metal atoms. As a consequence, cold Yb has been proposed for use in next-generation atomic clocks [2, 3], and the search for a permanent electric dipole moment (EDM) [4]. Exis- tence of an EDM is an indication of both parity viola- tion (which is already known from the weak interaction) and time-reversal symmetry violation in the fundamental laws of physics, and is one of the most important exper- iments in atomic physics today. As a consequence EDM measurements have been reported in

199 Hg [5],

133 Cs [6],

205 Tl [7], TlF [8],

174 YbF [9], etc. Both clock and EDM measurements gain from having a cold continuous beam of atoms that is separate from the cooling laser beams. For atomic clocks, a continuous beam avoids intermod- ulation or the Dick e?ect [10], seen in pulsed fountain clocks. For EDM experiments, the electric-?eld plates can be brought very close because there is no interfer- ence from any laser beams. Here, we demonstrate such a continuous beam by de- ?ection using a pair of 1D-optical molasses beams. Atoms emanating from a thermal source are ?rst cooled and slowed in a Zeeman slower. The molasses beams are in- clined at 45? , and chosen to be nearly resonant with one particular isotope. Thus, the de?ected atomic beam is isotopically pure, and free from both other isotopes and unslowed atoms. The de?ected atoms are probed at a distance of

160 mm from the molasses region. We verify that any selected isotope can be de?ected:

174 Yb as an example of an even isotope, and

171 Yb as an example of an odd isotope. A transient measurement after the mo- lasses beams are turned on shows a mean velocity of 15.55 m/s, and a longitudinal temperature of

41 mK. This tem- perature represents a factor of three improvement over our recent work in which atoms were launched vertically from a two dimensional magneto-optic trap (2D-MOT) [11]. Compared to the earlier experiment, the current set-up has the additional advantage of being easier to implement. II. EXPERIMENTAL DETAILS Many of the experimental details are similar to our earlier work in Ref. [11], and are presented here for com- pleteness. Yb has two cooling transitions―the strongly- allowed

1 S0 →

1 P1 transition at

399 nm, and the weakly- allowed

1 S0 →

3 P1 intercombination line at

556 nm―as shown in Fig. 1. In this study (as in our previous work), we have only used the former one. Though its relatively large linewidth of