PHYSICAL REVIEW A 81, 033424 (2010) Magnetic trapping of Yb in the metastable 3 P 2 state Kanhaiya Pandey, K. D. Rathod, Sambit Bikas Pal, and Vasant Natarajan * Department of Physics, Indian Institute of Science, Bangalore 560 012, India (Received 23 November 2009; published 29 March 2010) 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. DOI: 10.1103/PhysRevA.81.033424 PACS number(s): 37.10.Gh, 42.50.Wk, 32.10.Dk I. INTRODUCTION The metastable 3 P 2 state of Yb, with a lifetime of 15 s [1], is important as a possible clock transition (similar to the nearby 3 P 0 state [2]) and for quantum computation [3,4]. It is also potentially useful in experiments searching for a permanent electric dipole moment (EDM) because its closer proximity to states of opposite parity, compared to the ground state, enhances the EDM effect [5]. In addition, the paramagnetic nature of this state implies that the atomic EDM will be sensitive to the intrinsic EDM of the electron [6]. The ground state of Yb has total electronic angular momentum j = 0 and atoms cannot be magnetically trapped in this state. By contrast, atoms can be trapped in the metastable state because j = 2. The magnetically trapped atoms can be further cooled using evaporative cooling or used directly for measurements. Such atoms are already spin polarized, an important prerequisite for EDM measurements. Magnetic trapping allows the study of interatomic collisions [7,8], which could be important for clock applications or obtaining Bose-Einstein condensation (BEC) in the metastable state. BEC in the metastable state will differ from that of the spin-zero ground state [9–12], and magnetic trapping may provide a new route to observing BEC. The large Land´ e g factor of the 3 P 2 state makes it attractive for the study of dipolar magnetic interactions. Dipolar interactions have been studied in optical traps [13,14] but can be expected to be different in magnetic traps. In this work, we demonstrate magnetic trapping of 174 Yb in the 3 P 2 state. The relevant low-lying energy levels of Yb are shown in Fig. 1. As in the case of alkaline-earth-metal atoms, Yb has two transitions that can be used for laser cooling before loading the magnetic trap—the strongly allowed 1 S 0 → 1 P 1 transition at 399 nm and the weak 1 S 0 → 3 P 1 intercombina- tion line at 556 nm. Both lines have been used previously for laser cooling [15–18]. In this study, we use the strong 399-nm line. The atoms are first cooled and trapped in a magneto-optic trap (MOT). In contrast to recent experiments on trapping of Sr in the metastable state [19], where a significant fraction of atoms is automatically transferred into the metastable state during operation of the MOT, our experiment requires active pumping of the atoms into the metastable state by driving a * vasant@physics.iisc.ernet.in; URL: www.physics.iisc.ernet.in/ ∼vasant transition to the upper 3 S 1 state through the intermediate 3 P 1 state. Atoms from the 3 S 1 state partially decay into the 3 P 2 state. About 10 7 atoms are captured in the MOT, and more than 10% are transferred into the magnetic trap. The trap is formed by a spherical quadrupole magnetic field with an axial gradient of 110 G/cm. The trap has a lifetime of 1.5 s, limited primarily by the vacuum. We demonstrate both pulsed and continuous loading of the trap from the MOT. II. EXPERIMENTAL DETAILS The main experimental chamber is shown schematically in Fig. 2. The trapping is done in a pyrex chamber with seven intersecting viewports (octagonally placed) in the horizontal plane and two viewports in the vertical plane. All viewports are 30 mm in diameter. The vertical plane has a pair of anti- Helmholtz coils to produce the required quadrupole field. The glass chamber is connected to a stainless steel cross with a 40-l/s ion pump on one side and an all-metal valve on the other. This is connected to the Yb source through a small differential pumping tube. When the source is on, the pressure inside the main chamber is below 10 −8 torr, while the source side is up to two orders of magnitude higher. The source consists of metallic Yb in a quartz ampoule that is resistively heated to about 400 ◦ C. The source contains (6s 2 ) 1 S 0 Even parity (6s5d) 3 D 3 (6s5d) 3 D 1 (6s5d) 3 D 2 (6s7s) 3 S 1 Odd parity 3 P 0 (6s6p) 3 P 1 (6s6p) 3 P 2 (6s6p) 1 P 1 (6s6p) 556 nm 770 nm 680 nm 399 nm FIG. 1. (Color online) Low-lying energy levels of Yb showing the relevant transitions used in the experiment. 1050-2947/2010/81(3)/033424(4) 033424-1 ©2010 The American Physical Society