Raul A. Baragiola

Ion-induced electron emission from clean metals☆

Abstract We report recent experimental work on electron emission from clean polycrystalline metal surfaces under ion bombardment. We critically discuss existing theories and point out the presently unsolved problems.

Ionization of solids by heavy particles

Want to get experience? Want to get any ideas to create new things in your life? Read ionization of solids by heavy particles now! By reading this book as soon as possible, you can renew the situation to get the inspirations. Yeah, this way will lead you to always think more and more. In this case, this book will be always right for you. When you can observe more about the book, you will know why you need this.

Density and index of refraction of water ice films vapor deposited at low temperatures

The density of 0.5–3 μm thick vapor-deposited films of water ice were measured by combined optical interferometry and microbalance techniques during deposition on an optically flat gold substrate from a capillary array gas source. The films were of high optical quality with an index of refraction of 1.29±0.01 at 435.8 nm, a density of 0.82±0.01 g/cm3, and a porosity of 0.13±0.01. In contrast to previous studies, none of the measured properties exhibited any significant variation with growth rate or temperature over the range studied (0.6–2 nm/min, 20–140 K).

Sputtering of water ice surfaces and the production of extended neutral atmospheres

Plasma and UV photon bombardment of an icy object in the outer solar system can lead to ejection of atoms and molecules from the surface which can, in turn, produce an extended neutral atmosphere. We present new laboratory studies of the sputtering of water ice by keV ions (H+ through Ne+) made using a sensitive microbalance technique that allows measurements at very low ion fluences. These results for the sputtering yield of ice by keV O+ ions, the dominant sputtering agents in the Saturnian magnetosphere, are much larger than those used previously to model the neutral cloud associated with the icy satellites. The data presented are used to recalculate previously published sputtering rates for the icy satellites of Jupiter and Saturn, and for the E-ring grains at Saturn. The new results can account, in part, for the discrepancy between the predicted and observed OH cloud near Tethys in Saturns inner magnetosphere. We compare the yields induced by the incident ions to the recently measured UV photosputtering yield, and discuss possible synergism between UV photon and plasma ion induced erosion.

Ultraviolet photodesorption from water ice

Abstract The absolute desorption yield of low temperature (35–100 K) water ice under irradiation with Lyman-α (121.6 nm) photons. and its dependence on ice temperature and irradiation dose are measured. It is found that photodesorption can account for the absence of ice on grains in diffuse interstellar clouds, is an important factor determining the life of ice mantles in molecular clouds, and exceeds solar wind ion erosion and sublimation of ice grains in the outer solar system.

Cassini Finds an Oxygen–Carbon Dioxide Atmosphere at Saturn’s Icy Moon Rhea

Extraterrestrial Atmosphere The detection of oxygen in the atmospheres of Jupiters icy moons, Europa and Ganymede, and the presence of this gas as the main constituent of the atmosphere that surrounds Saturns rings, has suggested the possibility of oxygen atmospheres around the icy moons that orbit inside Saturns magnetosphere. Using the Ion Neutral Mass Spectrometer onboard the Cassini spacecraft, Teolis et al. (p. 1813, published online 25 November; see the Perspective by Cruikshank) report the detection of a very tenuous oxygen and carbon dioxide atmosphere around Saturns icy moon Rhea. As with other icy satellites, this atmosphere is maintained through the dissociation of surface molecules and ejection into the atmosphere as a result of Saturns magnetospheric radiation. Rhea’s atmosphere is maintained by chemical decomposition of surface water ice under irradiation from Saturn’s magnetosphere. The flyby measurements of the Cassini spacecraft at Saturn’s moon Rhea reveal a tenuous oxygen (O2)–carbon dioxide (CO2) atmosphere. The atmosphere appears to be sustained by chemical decomposition of the surface water ice under irradiation from Saturn’s magnetospheric plasma. This in situ detection of an oxidizing atmosphere is consistent with remote observations of other icy bodies, such as Jupiter’s moons Europa and Ganymede, and suggestive of a reservoir of radiolytic O2 locked within Rhea’s ice. The presence of CO2 suggests radiolysis reactions between surface oxidants and organics or sputtering and/or outgassing of CO2 endogenic to Rhea’s ice. Observations of outflowing positive and negative ions give evidence for pickup ionization as a major atmospheric loss mechanism.

CO2 synthesis in solid CO by Lyman-α photons and 200 keV protons

We have studied the synthesis of carbon dioxide from solid carbon monoxide at 16 K induced by photolysis with Lyman-α photons and by irradiation with 200 keV protons to quantitatively compare the effects of photolysis and ion irradiation on CO ice and to determine the importance of these processes in interstellar ice grains. The CO and CO2 concentrations during irradiation of an initially pure CO film evolve with fluence to a saturation value, a behaviour that is explained by a two-state model. Our results indicate that the initial CO2 production rates for both radiation processes are similar when normalized to the absorbed energy and that the solid CO2 abundance observed in the interstellar ices cannot be explained only by radiolysis and photolysis of pure solid CO.

Sputtering of water ice

We present results of a range of experiments of sputtering of water ice together with a guide to the literature. We studied how sputtering depends on the projectile energy and fluence, ice growth temperature, irradiation temperature and external electric fields. We observed luminescence from the decay of H(2p) atoms sputtered by heavy ion impact, but not bulk ice luminescence. Radiolyzed ice does not sputter under 3.7 eV laser irradiation.

Principles and mechanisms of ion induced electron emission

Abstract The mechanisms responsible for emission of electron from solids are described, separating them, when possible, into electron excitation, electron transport and cascade multiplication, and transmission through the surface barrier. Discussions include important energy quantities and quantum mechanical effects in the transport of slow electrons in the solid and through the surface barrier. Some new aspects not previously described are explored, such as how much information can be obtained by treating insulators as dense gases, electron loss from the projectile, differences between prompt and delayed excitation processes and final state effects in multiple electron emission.

Lunar surface: Sputtering and secondary ion mass spectrometry

We combine laboratory and Apollo observations to describe the sputtering of the lunar surface and the composition of the ejecta with special reference to O. The atmospheric inventory appears to be dominated by micrometeorite vaporization of lunar grains. Sputtering effects are observable in the local plasma due to ion ejection, in the extended atmosphere through energetic neutral ejection, and on grain surfaces through the chemical fractionation of the redeposited sputter-ejecta. Ionization of the micrometeorite-vapor also contributes to the local plasma.