Different dynamics of chiral and racemic L and DL serine crystals Evidenced by incoherent inelastic neutron and Raman scattering

Interest in chiral vs racemic amino acid forms stems from their different solid state properties associated to the packing arrangement that leads to starkly different physical behavior. Here we focus on the different dynamic properties of the chiral L form and racemic DL form crystals of serine, C3H7NO3 . Measuring incoherent inelastic neutron and Raman scattering over a wide temperature range we could asses a subtle dynamical transition in L serine near 150 K. The difference in the dynamic properties of the crystals of L and DL serine evidenced from our spectroscopic studies is in a good agreement with the different Cp T dependences and different structural strain of the two forms on cooling. Despite a higher bulk density, the molecular fragments in the crystals of L serine are more dynamic than in DL serine, and this manifests itself in the incoherent inelastic neutron and Raman spectra, as well as in a higher heat capacity, a higher thermal expansion coefficient, or in the NMR spectr

The 4#pi#-fragment-spectrometer FOBOS

The 4#pi# - fragment - spectrometer FOBOS developed for heavy-ion research at beam energies of 10 + 100 AMeV has been commissioned for physical experiments at the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research in Dubna. Based on the logarithmic detector principle, it is able to register charged fragments from protons up to heavy residual nuclei in a large dynamical range. Position-sensitive avalanche counters, axial ionization chambers and CsI(Tl) scintillation detectors are arranged in three concentric detector shells. An array of phoswich detectors is used as a more granular forward detector at narrow polar angles. The modular concept of FOBOS allows for different experimental application in the field of exclusive fragment spectroscopy at medium multiplicities. For illustration the fragment spectroscopy studies concerning the spontaneous fission process and the fragmentation of hot nuclei by means of the FOBOS set-up are considered. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman