<i>Public Drinking and Popular Culture in Eighteenth-Century Paris</i>, by Thomas Brennan

Johnson, Hubert C.

doi:10.3138/cjh.24.2.251

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“…The yield for solid D2 shows a somewhat stronger dependence than indicated by these models [14]. However, the dependence on the sublimation energy [12] is fulfilled only for an initial string temperature that leads to a yield about 1 order of magnitude too low [19]. Obviously, the existing spike treatments are not feasible for these volatile solids.…”

Section: A Single Point From Erents and Mccrackenmentioning

confidence: 97%

“…(The atoms in a molecular ion generate cylinders that overlap at the point of impact at the surface.) The cylindrical geometry means that the yield behavior might be explained by the cylindrical-spike model [6,12]. Since the sputtering yields for solid H2 as well as HD shown in Figs.…”

Section: A Single Point From Erents and Mccrackenmentioning

confidence: 99%

“…These dense cascades arise whenever the collision density is high or the binding of the target particles to the bulk sites is correspondingly weak. Sputtering under such spike conditions has been treated by several authors [11,12], and their models lead to a yield dependence on the primary energy similar to that of the nuclear stopping power squared. A parallel case for electronic sputtering was considered by Gibbs, Brown, and Johnson [6].…”

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Sputtering of solid hydrogenic targets by keV hydrogen ions

Stenum¹,

Schou²,

Ellegaard³

et al. 1991

Phys. Rev. Lett.

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The first sputtering measurements of the most volatile solid hydrogenic targets are reported. Bombardment of these targets by hydrogen and deuterium ions leads to erosion predominantly via electronic transitions. The magnitude of the yield depends strongly on the particular isotope. No existing theory for this electronic sputtering can explain the large yields that range from about 100 D2/H for solid deuterium up to 800 H2/H for solid hydrogen.PACS numbers: 79.20.Nc, 35.20.Gs Hydrogen isotopes are the most volatile materials [1,2] from which targets in vacuum may be produced. Their pronounced zero-point motion means that the vapor pressure, in particular for solid H2, is large even at liquidhelium temperature. Therefore, any attempt to conduct sputtering experiments with charged particles incident on these materials encounters severe difficulties. The primary beam power and the target temperature must be kept at such a low level that the mass loss from beaminduced evaporation is small compared with that from sputtering processes [3]. In contrast to evaporation, sputtering is characterized as the erosion of surfaces by individual particle impacts [4],The recent sputtering experiments on condensed gases including solid D2 demonstrate that the erosion predominantly takes place via electronic transitions, i.e., electronic sputtering [3,5,6]. Generally, the erosion of the surface follows a sequence of events initiated by the primary ion. The incident ion generates excited and ionized molecules along the path. Many of these excited states decay to repulsive states so that the molecules immediately dissociate. The repulsing atoms may initiate collision cascades in the material if the binding energy of the target particle to the lattice site is low compared with the energy release. When target particles close to the surface obtain sufficient kinetic energy, they can pass the surface barrier and be emitted from the material. Although the overall pattern described here is similar for electronic sputtering of the volatile condensed gases, the surface binding energy and the electronic deexcitations vary strongly from one condensed gas to another [3,[5][6][7].Electronic sputtering is relatively inefficient compared with ordinary (knockon) sputtering [3,7]. However, for most of the condensed gases the surface binding energy, which is usually considered to be the sublimation energy [8], is comparatively low. This means that the number of ejected particles per primary particle becomes relatively large, even when the sputtering is purely electronic. The solid hydrogenic targets constitute an extreme type of target material because of the low sublimation energy, which ranges from 8.65 meV for solid H2 up to 14.8 meV for solid T 2 [2]. Therefore, even for the least volatile stable isotope, solid deuterium, keV proton bombardment leads to yields higher than 100 D2 molecules per incident proton [9].The sublimation energy of the solid hydrogen isotopes is so low that one can expect nonlinear effects to occur even at very low stoppi...

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Section: A Single Point From Erents and Mccrackenmentioning

confidence: 97%

Section: A Single Point From Erents and Mccrackenmentioning

confidence: 99%

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