We present experiments on decelerating and trapping ammonia molecules using a combination of a Stark decelerator and a traveling wave decelerator. In the traveling wave decelerator, a moving potential is created by a series of ring-shaped electrodes to which oscillating high voltages (HV) are applied. By lowering the frequency of the applied voltages, the molecules confined in the moving trap are decelerated and brought to a standstill. As the molecules are confined in a true 3D well, this kind of deceleration has practically no losses, resulting in a great improvement on the usual Stark deceleration techniques. The necessary voltages are generated by amplifying the output of an arbitrary wave generator using fast HV amplifiers, giving us great control over the trapped molecules. We illustrate this by experiments in which we adiabatically cool trapped NH3 and ND3 molecules and resonantly excite their motion.
We report on the production, deceleration and detection of a SrF molecular beam. The molecules are captured from a supersonic expansion and are decelerated in the X 2 Σ + (v = 0, N = 1) state. We demonstrate the removal of up to 40% of the kinetic energy with a 2 meter long modular traveling-wave decelerator. Our results demonstrate a crucial step towards the preparation of ultracold gases of heavy diatomic molecules for precision spectroscopy.
As an important step towards an atomic parity violation experiment in one single trapped Ra + ion, laser spectroscopy experiments were performed with on-line produced short-lived 212,213,214 Ra + ions. The isotope shift of the 6 2 D 3/2 -7 2 P 1/2 and 6 2 D 3/2 -7 2 P 3/2 transitions and the hyperfine structure constant of the 7 2 P 1/2 and 6 2 D 3/2 states in 213 Ra + were measured. These values provide a benchmark for the required atomic theory. A lower limit of 232(4) ms for the lifetime of the metastable 6 2 D 5/2 state was measured by optical shelving.
A new test of Lorentz invariance in the weak interactions has been made by searching for variations in the decay rate of spin-polarized 20 Na nuclei. This test is unique to Gamow-Teller transitions, as was shown in the framework of a recently developed theory that assumes a Lorentz symmetry breaking background field of tensor nature. The nuclear spins were polarized in the up and down direction, putting a limit on the amplitude of sidereal variations of the form jðÀ up À À down Þj=ðÀ up þ À down Þ < 3  10 À3 . This measurement shows a possible route toward a more detailed testing of Lorentz symmetry in weak interactions.Lorentz invariance means that physical laws are independent of boosts and rotations. It is at the basis of all known interactions. In the weak sector relatively few tests of Lorentz invariance have been made, even though the understanding of the weak interactions has been crucial in developing the standard model. In this work we consider a new test that exploits the spin degrees of freedom in decay, searching for a dependence of the nuclear lifetime on the orientation of the nucleus. Recent theoretical work [1] enables relating the present test to other possible Lorentz symmetry tests in the weak interactions and put them in the overall framework developed by Kostelecký and coworkers [2]. Tests whether in neutral-meson [3] or neutrino [4] oscillations the combination of charge conjugation, parity and time reversal is conserved and tests of relativity exploiting the beta-decay endpoint spectrum [5] also concern the weak domain, however, they differ in nature.We write the relative variation in the -decay rate À asHere, À 0 is the standard model decay rate, with the velocity vector of the particle in units of the speed of light. The nuclear polarization of the parent nucleus is hĨi=I. A is the -asymmetry parameter in the standard model that violates parity. Other parameters in the decay of spin-polarized nuclei [1] are not relevant for this work. Lorentz invariance violation (LIV) appears in Eq. (1) with magnitudes 1
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