High precision measurements of the ground state hyperfine structure interval of muonium and of the muon magnetic moment

A new upper limit for the probability of spontaneous muonium to antimuonium conversion was established at P MM ≤ 8.2 · 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.

Rotational spectroscopy and molecular structure of 1,1,2-trifluoroethylene and the 1,1,2-trifluoroethylenehydrogen fluoride complex Rotational spectroscopy and dipole moment of cis-cis HOONO and DOONO

We present a superfluid hydrodynamic model for the increase in moment of inertia, ∆I, 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 ∆I 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 ∆I. This is likely to result from a (partial) breakdown of the adiabatic following approximation.

Intramolecular vibrational energy redistribution and conformational isomerization in vibrationally excited 2fluoroethanol: High-resolution, microwave-infrared double-resonance spectroscopy investigation of the asymmetric -CH 2 (F) stretch near 2980 cm−1 Microwave-infrared double-resonance spectroscopy has been used to probe the solvation environment and its influence on the rotational relaxation of a cyanoacetylene molecule embedded in a superfluid 4 He nanodroplet. The results support a model in which ͑within any given rotational state͒ the guest molecules are distributed over a set of spectroscopically inequivalent states which are most likely ''particle-in-a-box'' states originating from the confinement of the guest molecule within the droplet. Revisitation of previously collected microwave-microwave double-resonance data suggests that transitions between these states occur at a rate which is comparable to the rotational relaxation rate, but not fast enough as to produce motionally narrowed, homogeneous absorption lines. The relative intensities of the rotational lines in the microwave-infrared double-resonance spectra are observed to depend strongly on the average droplet size. In the large droplet limit we can explain the observed pattern by invoking a ''strong collision'' regime, i.e., one in which the branching ratios of the rotational relaxation do not depend on the initial rotational state. For small droplets we speculate that, because of finite size effects, the density of ͑surface͒ states may become discontinuous, producing deviations from the ''thermal'' behavior of the larger systems.