arXiv subjects
Publications and source records attributed to I. Reinhard.
The pressure shifts of the $3s4s^3S_1 \to 3s3p^3P_{0,1,2}$ transition of magnesium atoms immersed in superfluid helium have been measured at $(1.3\pm0.1 )$K between saturated vapour pressure and $24 $bar. The wavelength is blue shifted linearly by $(0.07\pm0.01) \frac{nm}{bar}$. This value can be satisfactorily described in the framework of the standard bubble model.
We present a superfluid hydrodynamic model for the increase in moment of inertia, $ΔI$, of molecules rotating in liquid $^4$He. The static inhomogeneous He density around each molecule (calculated using the Orsay-Paris liquid $^4$He density functional) is assumed to adiabatically follow the rotation of the molecule. We find that the $ΔI$ values created by the viscousless and irrotational flow are in good agreement with the observed increases for several molecules [ OCS, (HCN)$_2$, HCCCN, and HCCCH$_3$ ]. For HCN and HCCH, our model substantially overestimates $ΔI$. This is likely to result from a (partial) breakdown of the adiabatic following approximation.
Purely rotational transitions of a molecule, such as HCCCN, embedded in large $^4$He clusters have been detected for the first time. The saturation behavior shows that, in contrast to previous expectations, the microwave line profiles are dominated by inhomogeneous broadening mechanisms. Spectral holes and peaks produced by microwave-microwave double resonance have widths comparable to those of single resonance lines, indicating that relaxation occurs among quantum states of the inhomogeneous distribution of each rotational level, at a rate approximately 10 times faster than rotationally inelastic relaxation.
The 1s-2s interval has been measured in the muonium ({$μ^+e^-$}) atom by Doppler-free two-photon laser spectroscopy. The frequency separation of the states was determined to be 2 455 528 941.0(9.8) MHz in good agreement with quantum electrodynamics. The muon-electron mass ratio can be extracted and is found to be 206.768 38(17). The result may be interpreted as measurement of the muon-electron charge ratio as $-1- 1.1(2.1)\cdot 10^{-9}$.
A new upper limit for the probability of spontaneous muonium to antimuonium conversion was established at ${\rm P_{M\bar{M}}} \leq 8.2 \cdot 10^{-11}$ (90%C.L.) in 0.1~T magnetic field, which implies consequences for speculative extensions to the standard model. Coupling parameters in R-parity violating supersymmetry and the mass of a flavour diagonal bileptonic gauge boson can be significantly restricted. A Z$_8$ model with radiative mass generation through heavy lepton seed and the minimal version of 331-GUT models are ruled out.
A new experiment has been set up at the Paul Scherrer Institut to search for muonium to antimuonium conversion. No event was found to fulfil the requested signature which consists of the coincident detection of both constituents of the antiatom in its decay. Assuming an effective (V-A)$\times$(V-A) type interaction an improved upper limit is established for the conversion probability of ${\rm P_{M\bar{M}}} \leq 8 \cdot 10^{-9}$ (90%C.L.), which is almost two orders of magnitude lower compared to previous results and provides a sensitive test for theoretical extensions of the standard model.
A new experimental search for muonium-antimuonium conversion was conducted at the Paul Scherrer Institute, Villigen, Switzerland. The preliminary analysis yielded one event fulfilling all required criteria at an expected background of 1.7(2) events due to accidental coincidences. An upper limit for the conversion probability in 0.1 T magnetic field is extracted as $8 \cdot 10^{-11}$ (90% CL).
A new result from searching for muonium to antimuonium conversion is reported which sets an upper limit on the coupling constant in an assumed $(V-A) \times (V-A)$ type interaction of $G_{M\bar{M}} \leq 3\cdot 10^{-3} G_F$ ~ (90% C.L.). A particular Z_8 and a minimal 331 GUT model can be ruled out. Further new and stringent limits can be set for masses of bileptonic gauge bosons and $λ$ parameters in R-parity breaking supersymmetric models.