83 research outputs found
Conductivity mechanism probed by ion transmission through nanocapillaries during the discharging process
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Ionization of small molecules induced by H+, He+, and N+ projectiles: comparison of experiment with quantum and classical calculations
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Őz állományok légi létszámbecslésének tapasztalatai mezei élőhelyen = First Experiences on the Aerial Estimation of Roe Deer Population Numbers in Open Agricultural Habitats
Formation of anions and cations via a binary-encounter process in OH+ + Ar collisions: The role of dissociative excitation and statistical aspects
Bombardment of CO ice by cosmic rays: I. Experimental insights into the microphysics of molecule destruction and sputtering
We present a dedicated experimental study of microscopic mechanisms
controlling radiolysis and sputtering of astrophysical ices due to their
bombardment by cosmic ray ions. Such ions are slowed down due to inelastic
collisions with bound electrons, resulting in ionization and excitation of ice
molecules. In experiments on CO ice irradiation, we show that the relative
contribution of these two mechanisms of energy loss to molecule destruction and
sputtering can be probed by selecting ion energies near the peak of the
electronic stopping power. We have observed a significant asymmetry, both in
the destruction cross section and the sputtering yield, for pairs of ion
energies corresponding to same values of the stopping power on either side of
the peak. This implies that the stopping power does not solely control these
processes, as usually assumed in the literature. Our results suggest that
electronic excitations represent a significantly more efficient channel for
radiolysis and, possibly, also for sputtering of CO ice. We also show that the
charge state of incident ions as well as the rate for CO production in the
ice have negligible effect on these processes.Comment: Accepted for publication in Ap
Cohomological characterizations of projective spaces and hyperquadrics
We confirm Beauville's conjecture that claims that if the p-th exterior power
of the tangent bundle of a smooth projective variety contains the p-th power of
an ample line bundle, then the variety is either the projective space or the
p-dimensional quadric hypersurface.Comment: Added Lemma 2.8 and slightly changed proof of Lemma 6.2 to make them
apply for torsion-free sheaves and not only to vector bundle
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