Formation and fragmentation dynamics of superexcited molecules

A series of experimental studies on superexcited smallmolecules have been performed giving new information on theformation and fragmentation dynamics of small superexcitedmolecules. Highly monochromatized synchrotron radiation hasbeen applied in the 5-30 eV energy region, corresponding tovalence shell excitation, and in the 60-600 eV region,corresponding to core shell excitation, to reach these neutralstates above the ionization potential. The superexcited states in the irradiated N2and CO and molecules have been probed in thevalence excitation region by detecting dispersed fluorescencewith vibrational resolution emitted from subsequently producedfragments using a liquid nitrogen cooled CCD detector togetherwith a grating spectrometer. The measurements have resulted inthe discovery of non-Rydberg doubly excited resonances. Thesestates are reached directly by simultaneous promotion of twovalence electrons to in space close lying orbitals or viapotential curve crossings. The experimental results have beencomparedwith the results from extensive calculations. A time-of-flight mass spectrometer has been built and usedto measure branching ratios and kinetic energy distributions ofionic fragments produced from molecules in core excited valenceand Rydberg states. The measurements have been performed on CO,OCS and CS2molecules using different coincidence and angularresolved techniques. The results include new information on thegeometry and fragmentation dynamics of these highly excitedmolecules. Monte Carlo simulations have been performed tointerpret some of the data suggesting new models for thefragmentation dynamics. Strong evidences for state and siteselectivity in the fragmentation dynamics of core excitedmolecules have been obtained.NR 2014080

Design and test of a beam line for extraction of slow antiprotons from a multi-ring electrode ion trap

A new monoenergetic slow antiproton beam facility has recently been installed at the CERN Antiproton Decelerator (AD). The system is designed to deliver pulsed or continuous antiproton beams in the 10-1000 eV energy region which is suitable for various interesting atomic and molecular spectroscopic and collision studies. The antiprotons obtained from the AD are slowed down to around 100 keV by passing the Radio Frequency Quadrupole Decelerator (RFQD) and then captured in a multi-ring electrode ion trap. After electron cooling down to a few eV, the antiprotons will be extracted out from the trap into a collision chamber via a differential pumping system. In this paper, we present recent results in which the antiproton capture and cooling phases of this scheme have been successfully demonstrated. Furthermore, the design and tests of the extraction and differential pumping system are presented. (8 refs)