Search results for "Atomic and Molecular Collisions"
showing 2 items of 2 documents
Temperature dependence of sodium and ionized calcium resonance lines perturbed by helium
2014
International audience; Traces of heavy metals in cool DZ white dwarf stars may be attributed to the accretion of circumstellar dust thought to originate from tidal disruption of rocky parent bodies. Spectra of such stars therefore provide a unique opportunity to study the composition of extrasolar planetary systems. The determination of metal abundances from stellar spectra depends on stellar atmospheric parameters and an accurate prior knowledge of the collision broadening of the line profiles by the most common constituents of the stellar atmosphere. For this purpose, we present theoretical absorption spectra of Na and Ca+ broadened by He for the conditions prevailing in cool white dwarf…
Energy-loss straggling of 2-10 MeV/u Kr ions in gases
2013
Measurements have been performed on a time-of-flight setup at the Jyväskylä K130 cyclotron, aiming at energy-loss straggling of heavy ions in gases. Theoretical predictions based on recently developed theory as well as an empirical interpolation formula predict that straggling can be more than ten times higher than Bohr straggling in the MeV/u regime. Our measurements with up to 9.3 MeV/u Kr ions on He, N2, Ne and Kr targets confirm this feature. Our calculations show the relative contributions of linear straggling, bunching including packing, and charge exchange. Our results for stopping cross sections are compatible with values from the literature. Funding Agencies|EU||Academy of Finland …