Mass measurements of very neutron-deficient Mo and Tc isotopes and their impact on rp process nucleosynthesis

The masses of ten proton-rich nuclides, including the N=Z+1 nuclides ??Mo and ??Tc, were measured with the Penning trap mass spectrometer SHIPTRAP. Compared to the Atomic Mass Evaluation 2003 a systematic shift of the mass surface by up to 1.6 MeV is observed causing significant abundance changes of the ashes of astrophysical x-ray bursts. Surprisingly low α separation energies for neutron-deficient Mo and Tc are found, making the formation of a ZrNb cycle in the rp process possible. Such a cycle would impose an upper temperature limit for the synthesis of elements beyond Nb in the rp process.     

Resonant enhancement of neutrinoless double-electron capture in 152Gd

In the search for the nuclide with the largest probability for neutrinoless double-electron capture, we have determined the Q(??) value between the ground states of (152)Gd and (152)Sm by Penning-trap mass-ratio measurements. The new Q(??) value of 55.70(18) keV results in a half-life of 10(26) yr for a 1 eV neutrino mass. With this smallest half-life among known 0ν?? transitions, (152)Gd is a promising candidate for the search for neutrinoless double-electron capture.     

COLTRAP: a 22-pole ion trapping machine for spectroscopy at 4 K

Two similar 4 K 22-pole trapping machines have been recently completed in our laboratory. As a first experimental test in one of them, CH ₅ ⁺ and H₃O⁺ ions have been trapped in the presence of helium gas at 3.8 K and the kinetics and temperature dependence of He tagging investigated. A first shell closure with 5 and (3 + 2) attached He atoms, respectively, is observed for both species. Applying IR radiation in the 3 μm region, helium attachment to CH ₅ ⁺ is hindered by exciting CH-stretches of CH ₅ ⁺ prior to attachment. The resulting spectroscopic signal shows that the kinetic temperature of the stored CH ₅ ⁺ ensemble is below 12 K.     

ChemInform Abstract: 3s-Gd2C2Br2, an Isomorph with a New Stacking Sequence

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