High-Precision Spectroscopy of Forbidden Transitions in Ultracold 4He and 3He

Florian Jessen, M. Knufinke, S. C. Bell +13 more

B. H. McGuyer, Mickey McDonald, Geoffrey Z. Iwata +1 more

Kees Steinebach

Although the Standard Model is highly successful, it is not complete. One approach to searching for effects beyond our current understanding of physics is to measure finite-size effects in simple atomic systems through high-precision spectroscopy. In this thesis, we present new measurements of the 2 3S1 -> 2 1S0 transition in 3He and 4He with the highest precision achieved to date. We perform these measurements in ultracold trapped gases in the quantum-degenerate regime. These spectroscopic measurements are used to determine the difference in charge radius between the helion and the alpha particle, the nuclei of 3He and 4He, respectively. By comparing the extracted charge-radius difference with values obtained from other experiments, we test isotope-shift calculations and bound-state quantum electrodynamics.

Yujun Wang, Paul S. Julienne

U. Fröhlich

In this work, the setup of an experiment aimed at high-precision laser spectroscopy of ultracold molecular hydrogen ions, started at the University of Konstanz in 1999 [1,2], was continued and first results were obtained. In particular, a new linear rf trap and a new trap supply electronics were built, the latter being capable of driving the linear rf trap with a maximum rf amplitude of > 1000V at a frequency of 14.2MHz. This made possible the simultaneous trapping of a large mass range (2u For laser cooling of Be+ ions, doubly resonant sum-frequency generation (DR-SFG) of 313nm laser light was performed between a resonantly frequency-doubled monolithic Nd:Yag laser and a Ti:sapphire laser, emitting at 532 and 760nm wavelength, respectively. An output power of P_UV > 100mW was achieved at 313nm wavelength, with a high spectral purity (rms short-term frequency fluctuations With this experimental setup, sympathetic cooling of N+, BeD+, BeH+, 4He+, HD+, and D+ ions by the laser-cooled Be+ ions was demonstrated, using laser-cooled fluorescence mass spectrometry (LCF-MS) to detect the sympathetically cooled species. Accordingly, sympathetic cooling at a minimum mass ratio of m(H2+)/m(Be+) = 0.22 was shown to be possible with both the sympathetically and laser-cooled ions in a cloud-like state. This points out the incorrectness of the theoretical lower limit m_SC/m_LC = 0.53 which was predicted in Ref.[3]. Here, the subscripts SC and LC denote the sympathetically and the laser-cooled species, respectively. In a further experiment, almost pure Be+ ion plasmas were laser-cooled down to temperatures in the milli-Kelvin range, leading to the crystallization of the Be+ ion plasmas. The outer shapes of different-sized Be+ ion crystals in a fully anisotropic trap potential were compared with the charged fluid predictions, showing good agreement at sufficiently large numbers of Be+ ions. By fitting Voigt profiles to the measured fluorescence signal, a typical temperature T(Be+) of 30mK was estimated for the Be+ ions. Finally, an ultracold sample of 4He+ ions [T(He+) approximately 40mK] was produced for the first time by sympathetic crystallization of the 4He+ ions. This may open up perspectives for the high-precision laser spectroscopy of 4He+ (and 3He+). [1] T.K.W. Boley, Diplomarbeit, Universitat Konstanz (1999) [2] H. Schnitzler, Dissertation, Universitat Konstanz (2001) [3] T. Baba and I. Waki, Appl.Phys.B, 74, 375-382 (2002)

J. P. Davis, J. Pollanen, Hyun Joon Choi +2 more