We studied the dynamic properties of ion guiding through nanocapillaries in insulating polyethylene terephthalate. The angular distribution of the transmitted ions was measured as a function of the charge deposited on the sample surface, which is a measure of time. The time evolution of the angular transmission profiles was acquired for the capillary diameters of 200 and 400 nm. The tilt angle was varied from 0°to 6.5°. The transmission profiles appear as a superposition of essentially three localized peaks which exhibit significant changes in intensity as time varies. This observation provides evidence for the formation of temporary charge patches produced in the interior of the capillary besides the primary charge patch created in the entrance region.
Strong X-ray and far-ultraviolet emission from comets is the direct result of charge exchange reactions of solar wind ions with the neutral coma of comets. Here we report experimental state-selective cross sections of electron capture and use these to predict cometary line emission. Our results show that helium line ratios are a direct diagnostic of the solar wind velocity, while their absolute intensities are linked to the local density of the solar wind. Comparison with observations of Hale-Bopp yields a velocity of 220 km s Ϫ1 and a helium density of 0.6 cm
Ϫ3, and observations of Hyakutake show that it interacted with a faster wind of 375 km s Ϫ1 and a helium density of 10 Ϫ3 cm
Ϫ3. The potential of line emission by heavy minor ions is also demonstrated. Spectral lines with energies greater than 650 eV contain a wealth of information on the original composition of the wind, while lines at lower energies are used best to study the interaction processes themselves.
We demonstrate that the formation of negative hydrogen ions (H -) occurs in a wide class of atomic and molecular collisions. In our experiments, Hemission from hydroxyl cations and acetone molecules was observed in keV-energy collisions. We show that hydride (H -) anions are formed via direct collisional fragmentation of molecules, followed by electron grabbing by fast hydrogen fragments. Such general mechanism in hydrogen-containing molecules may significantly influence reaction networks in planetary atmospheres and astrophysical media and new reaction pathways may have to be added in radiolysis studies.
The guiding of multiply charged Ne 7+ ions through nanocapillaries in highly insulating polymers was investigated. Highly parallel capillaries with a density of Շ10 7 cm −2 and diameters of Շ100 nm were utilized. The widths of the angular profiles were measured for Ne 7+ ions transmitted through the capillaries. Moreover, the fractions of transmitted ions were measured as a function of the capillary tilt angle. The results were used to evaluate the characteristic guiding angle, which is a measure of the guiding power specifying the ability of a material to guide ions. Results for the polyethylene terephthalate ͑PET͒ and polycarbonate ͑PC͒ samples were compared to verify the role of the material of the capillary wall. Relatively high projectile energies of up to 50 keV were used to extend the validity of previous scaling laws based on the projectile charge-to-energy ratio. The profile widths and the guiding angles for both polymers are found to compare well with the scaling laws showing that PET and PC have nearly equal guiding properties.
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