Surface-induced dissociation and chemical reactions of C₂D₄⁺ on stainless steel, carbon (HOPG), and two different diamond surfaces

Abstract

Surface-induced interactions of the projectile ion C 2 D 4 ϩ with room-temperature (hydrocarbon covered) stainless steel, carbon highly oriented pyrolytic graphite (HOPG), and two different types of diamond surfaces (O-terminated and H-terminated) were investigated over the range of incident energies from a few eV up to 50 eV. The relative abundance of the product ions in dependence on the incident energy of the projectile ion [collision-energy resolved mass spectra, (CERMS) curves] was determined. The product ion mass spectra contained ions resulting from direct dissociation of the projectile ions, from chemical reactions with the hydrocarbons on the surface, and (to a small extent) from sputtering of the surface material. Sputtering of the surface layer by low-energy Ar ϩ ions (5-400 eV) indicated the presence of hydrocarbons on all studied surfaces. The CERMS curves of the product ions were analyzed to obtain both CERMS curves for the products of direct surface-induced dissociation of the projectile ion and CERMS curves of products of surface reactions. From the former, the fraction of energy converted in the surface collision into the internal excitation of the projectile ion was estimated as 10% of the incident energy. The internal energy of the surface-excited projectile ions was very similar for all studied surfaces. The H-terminated room-temperature diamond surface differed from the other surfaces only in the fraction of product ions formed in H-atom transfer surface reactions (45% of all product ions formed versus 70% on the other surfaces). O ver the last two decades, research on lowenergy ion-surface interactions has grown substantially. Attention has been focused on selected physical and chemical processes stimulated by the impact of slow ions with incident energies up to 100 eV [1][2][3][4][5]. The amount of incident energy converted during these collisions into projectile internal energy is of the order of a typical chemical bond energy in molecules and thus can cause bond dissociation. As such, studies of slow ion-surface interaction can yield valuable information pertaining to the projectile or to the surface or to the nature of the ion-surface interaction.

Low-Energy Ionic Collisions at Molecular Solids

“…These reaction products disappeared when the HOPG surface was heated to 600 °C as the adsorbed hydrocarbon layer was removed by heating and elastic scattering became dominant. It was found that the hydrogen abstraction reactions and subsequent fragmentations of C 2 D 4 + at hydrophobic H-diamond and hydrophilic O-diamond surfaces were very similar . The collision of C 3 H n ( n = 2–8) ions and their deuterated analogues could not execute carbon chain buildup reactions at room temperature .…”

“…Herman and co-workers have done a series of experiments with small hydrocarbon (C 1 –C 3 ) projectile ions at collision energies of <50 eV. ,− The reaction products observed due to the collision of small hydrocarbon ions CH n + and C 2 H m + and their D isotopic variants on HOPG surfaces at room temperature showed hydrogen atom transfer and carbon chain buildup reaction. ,, The actual reactions occur between adsorbed hydrocarbons and projectile ions. Subsequent dissociation of the reaction products occurs in addition to fragmentation of the projectile ions.…”

“…It was found that the hydrogen abstraction reactions and subsequent fragmentations of C 2 D 4 + at hydrophobic H-diamond and hydrophilic Odiamond surfaces were very similar. 319 The collision of C 3 H n (n = 2−8) ions and their deuterated analogues could not execute carbon chain buildup reactions at room temperature. 146 However, the radical cations C 3 H 8 + and C 3 H 6 + showed fragmentation and products of H atom transfer between the projectile ion and adsorbed hydrocarbon on the surface.…”

Modeling the intrusion of molecules into graphite: Origin and shape of the barriers

“…The interaction of molecular projectiles with fusion-relevant wall materials has been subject to a variety of experimental studies conducted in the last years [10–20] . Especially the groups of Hermann and of Märk conducted several mass-spectrometric experiments with respect to molecule/surface interactions [12,13,16–20] . They let deuterated hydrocarbon ions interact with stainless steel [10,19] , carbon [11–15,17–20] , beryllium [18] and tungsten [16,18] .…”

“…Especially the groups of Hermann and of Märk conducted several mass-spectrometric experiments with respect to molecule/surface interactions [12,13,16–20] . They let deuterated hydrocarbon ions interact with stainless steel [10,19] , carbon [11–15,17–20] , beryllium [18] and tungsten [16,18] . All of these surfaces are of relevance in thermo-nuclear fusion research.…”