Astronomy and Astrophysics – Astronomy
Scientific paper
May 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011iaus..280p.119c&link_type=abstract
The Molecular Universe, Posters from the proceedings of the 280th Symposium of the International Astronomical Union held in Tole
Astronomy and Astrophysics
Astronomy
Scientific paper
Recent experiments have shown that films of molecules such as nitrous oxide, propane etc. spontaneously harbour very high electric fields exceeding 108 Vm-11 . This arises through dipole alignment with polarization at the film surface, giving rise to large voltages at the surface. Potentials are measured with a cold electron beam technique using the ASTRID synchrotron at Aarhus. The electric field within the film is constant. Since a spontaneous field is generated the films show ferroelectric properties. Figure 1 shows the amount of potential added per added monolayer (ML) of material, in this case on a gold surface. The absolute value of potential and the field generated is independent of the nature of the surface. If we assume the 'standard' onion skin model of mantle accretion on grains, then the outer layer of grains will be composed of almost pure CO. If a large fraction of CO is adsorbed into the mantle, as is the case in B682, the mantle of pure CO will be typically 10-100 MLs thick. We mark, in Figure 1, the position of CO with respect to dipole moment. It would therefore seem highly probable that CO would show dipole alignment, although we have not yet been able to measure this for the purely technical reason that our apparatus will not operate below 38K and CO requires 22K to condense. Thus the surface of such grains would show a positive potential, given that the O-atom sticks up (McCoustra, private communication). The polarization on the surface is expected to be >10-4 Cm-2, giving 75 apparent charges on a 0.1 micron radius grain, which will decay as electrons are captured. Coupled with an electric field within the CO ice mantle of > 10^7 Vm-1, this may have interesting implications in grain properties and their associated chemistry. This will be discussed in our contribution.
Balog R.
Cassidy A. M.
Field David
Jones Nathan
Plekan O.
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