Chemistry Division

Optical and Laser spectroscopy of Th-229 Nuclear isomer

Atomic clocks that form the backbone of timing and GPS system are enabling technology.  Th-229 nucleus has a low-energy isomeric state that could be used as a nuclear clock oscillator with great potential to be more accurate, robust, and portable than its atomic counterpart.  We are making spectroscopy measurement to determine the wavelength of the nuclear transition and demonstrate nuclear laser spectroscopy with a large number of Th-229 nuclei embedded in solid.

Atom Trapping

The team has also developed an efficient method of trapping radioactive atoms for both fundamental and applied research. Our system uses a high-efficiency magneto-optical trap (MOT) that is coupled to an off-line mass separator. Once the desired atoms are trapped they can be detected with high sensitivity or transferred to another trap where a variety of experiments are performed, including Parity violation in beta-decay to search for new physics beyond the Standard Model and Ultrasensitive detection for nonproliferation and environmental/dating applications.

Our system uses a high-efficiency magneto-optical trap (MOT) that is coupled to an off-line mass separator. Once the desired atoms are trapped they can be detected with high sensitivity or transferred to another trap where a variety of experiments are performed. We are presently pursuing the following research areas:

Parity violation in beta-decay
We have recently demonstrated the trapping of polarized 82Rb (t1/2=75 s) to observe the parity-violating beta-nuclear spin correlation (setup and data). A 1% measurement of this correlation is planned to further test the maximal parity violating nature of the weak interaction and to search for new physics beyond the Standard Model.

Ultrasensitive detection
For nonproliferation and environmental/dating applications, we are using the high selectivity and sensitivity of the mass separator–MOT system to detect small numbers of selected radioisotopes. To date we have trapped 135Cs (t1/2=2 x 10^6 y) and 137Cs (t1/2=30 y) and measured their isotopic ratio for the first time in a MOT with sensitivities as small as 10^7 atoms per sample.

Updated October 2014 under LALP 05-096

Near-infrared picture of a fluorescing cloud of Cs atoms trapped in a MOT.

Near-infrared picture of a fluorescing cloud of Cs atoms trapped in a MOT.

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