Secondary Molecular Ion Emission In Binary Projectile-Surface Collisions (original) (raw)
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Molecular secondary ion emission from binary collisions
Surface Science, 2004
Secondary ions, produced by neutral 1.0 MeV argon beam impact on Al 2 O 3 and LiF thin films, are analyzed by a XY-TOF detection system. Angular distributions and initial velocities are simultaneously determined for ionized species originating from the bulk or from the adsorbate layer. The employed XY-TOF spectrometer was designed to measure accurately radial and axial velocity measurements of positive and negative secondary ions with mass <50 u and desorbed from the surface material in the 100-eV energy range. The analysis shows that high velocity diatomic and triatomic molecules can be also emitted in a process similar to the one involving atomic secondary ions, in which energetic binary collisions causes emission perpendicularly to the beam direction. The initial velocity distribution analysis is shown to be helpful in the identification of chemical species lying either on surface or in the bulk material. Ó 2004 Published by Elsevier B.V.
AIP Conference Proceedings, 1993
Absolute doubly differential cross sections for electron emission are presented for 0.5 MeV/u multi-charged ion impact on helium, neon, and argon targets. For the helium target, Bq*, Cq+ (q = 2-5) and Oq+, Fq* (q = 3-6) projectiles were studied; for neon and argon, only Cq+ (q = 2-5) projectiles were used. Electron emission for 10°___ ® .<_ 60°was studied. The measured cross sections were assumed to scale as the square of an effective projectile charge, Zeff, which was determined as a function of emitted electron energy and angle. For distant collisions (low emitted electron energies), we find that Zeff = q for small q and Zeff < q for the highest values of q investigated. For sufficiently close collisions (above the binary encounter peak), Zeff > Z and increases as q decreases. This is true for ali angles and targets investigated.
Dynamics of secondary ion emission: Novel energy and angular spectrometry
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2002
A new spectrometer has been developed based on the combination of standard time-of-flight technique and position sensitive delay line detectors. The basic features of the spectrometer, particularly of the multi-hit capable detector, are described. To demonstrate the performance of this new system, the dynamic emission characteristics, i.e. the threedimensional velocity distribution, of desorbed H þ 2 from Al target by Ar 0 impact (570 keV) is presented. It is found that the desorption yield is maximum for radial and axial emission velocities at 1.2 and 12 km/s respectively, corresponding to 1.5 eV ions emitted at 57°to normal (following the projectile radial direction). The initial energy distribution spreads out over 16 eV. Ó
Molecular ion emission from single large cluster impacts
We investigated the emission of the secondary ions stimulated by single impacts of 136 keV Au 400 4+ projectiles. The study was carried out on targets of glycine, phenylalanine, and C 60 . In addition, a target of C 60 was examined with 18 keV C 60 + projectiles. The experiments were performed in the event-by-event bombardment/detection mode. The secondary ions were identified with linear time-of-flight mass spectrometer equipped with an 8-anode detector. The Au 400 4+ projectile induces abundant multi-ion emission, for instance the average number of detected ions (atomic, fragment, molecular and cluster ions) emitted per event from glycine target is 12.5. The glycine intact molecular ion (Gly À ) yield is 1.14. The bombardment of a C 60 target results in the efficient emission of multiple intact C 60 À (total yield is 0.15).
RADIAL VELOCITY MEASUREMENTS OF SECONDARY MOLECULAR IONS IN keV AND MeV BOMBARDMENT
RBsum6 -Les ions secondaires formCs B partir d'6chantillons solides d'insuline bovine (5733~) ont Ctt produits par bombardement au moyen de particules B haute tnergie (MeVIu) et B faible Cnergie (-keV/u). Les distributions de vitesses ont CtC mesurges dans des spectromttres par temps de vol au moyen de plaques dkflectrices plactes dans la rCgion fibre de champ des appareils. Pour le bombardement B haute Cnergie, une corrClation a CtC observCe entre l'angle d'tjection moyen des ions molCculaires et la direction de l'ion incident.
Surface Secondary-Electron and Secondary-Ion Emission Induced by Large Molecular Ion Impacts
International Journal of Mass Spectrometry and Ion Processes, 1993
This paper presents results on secondary ion and secondary electron yields under impact of large ions at 18 keV and with 100 &amp;amp;lt; m/z &amp;amp;lt; 70 000 on a CsI-coated surface. Ratios of secondary electron emission to secondary ion emission have been measured and it is shown that the negative secondary ion yield is much larger than the electron yield.
Secondary ion emission induced by multicharged 18-keV ion bombardment of solid targets
Physical Review Letters, 1988
Solid targets of Si02, CsI, and organic layers of phenylalanine have been bombarded by multicharged Ar~+ ions with 1~q~11. The secondary-ion yield has been measured as a function of the incident charge state. No charge-state dependence was observed for most of the atomic and molecular ions, which were identified by time-of-flight mass spectrometry. In contrast, the H-ion emission is strongly dependent on the incident charge state.
Role of Auger-type emission from diatomic molecular targets interacting with fast multicharged ions
Physical Review A, 2009
Multiple electron emission in collisions between bare multiply charged ions and diatomic molecules is studied. The role played by Auger-type emission in cross sections for fixed number of ejected electrons is investigated. It is shown that this postcollisional reaction gives the main contribution to these cross sections at high enough impact velocities. This behavior is accentuated as the ionization degree increases.
Ion excitation in binary collisions
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1996
The impact parameter dependence of the energy lost by a fast many-electron ion in binary collision with an atom were studied theoretically. The electronic excitation and ionisation of both ion and atom were considered within the first Born approximation, while exchange of electrons was neglected. The effective charge of the interaction was analysed as a function of ion atomic number, number of electrons, ion velocity and mean excitation energy.