Multiply Charged Ar Ions Research Articles

Narrow band vacuum ultraviolet radiation, produced by fast conical discharge

The article presents the experimental study of discharges in a conical cavity, filled with Ar at pressure 80 Pa. The electrical current driver (inductive storage with plasma erosion opening switch) supplies to the load electrical current pulse with growth rate about 1012 A s−1 and maximal value 30–40 kA. The convergent conical shock wave starts from the inner surface of the discharge cavity and collapses in ‘zippering’ mode. The pin hole camera imaging with MCP detector (time resolution 5 ns) have demonstrated the appearance of effectively fast moving compact plasma with visible velocity v = (1.5 ± 0.14) × 107 cm s−1. Plasma emits narrow band radiation in the spectral range of Rydberg series transitions of Ar VII, Ar VIII with quantum number up to n = 9 (wavelength about 11 nm). The intensity of radiation is comparable with the total plasma emission in the range 10–50 nm. Charge exchange between multiply charged Ar ions and cold Ar atoms of working gas is proposed as the possible mechanism of the origin of the radiation.

Channels of Potential Energy Dissipation during Multiply Charged Argon-Ion Bombardment of Copper

The dissipation of potential energy of multiply charged Ar ions incident on Cu has been studied by complementary electron spectroscopy and calorimetry at charge states between 2 and 10 and kinetic energies between 100 eV and 1 keV. The emitted and deposited fractions of potential energy increase at increasing charge state, showing a significant jump for charge states q>8 due to the presence of L-shell vacancies in the ion. Both fractions balance the total potential energy, thus rendering former hypotheses of a significant deficit of potential energy obsolete. The experimental data are reproduced by computer simulations based on the extended dynamic classical-over-the-barrier model.

Interaction of slow multiply charged Ar ions with a LiF insulator surface

We have investigated electron emission for impact of slow multiply charged Ar ions on an atomically clean and flat insulating LiF(001) surface. Time-of-flight spectra and the number of emitted electrons have been determined in coincidence for grazing scattering of Arq+ projectiles from LiF. By relating projectile energy loss to kinetic electron emission we were able to determine contributions from potential electron emission even in the presence of a considerable number of kinetically excited electrons. [DOI: 10.1380/ejssnt.2006.388]

Separation of Potential and Kinetic Electron Emission for Grazing Impact of Multiply Charged Ar Ions on a LiF(001) Surface

Projectile time-of-flight spectra and the number of emitted electrons have been determined in coincidence for grazing scattering of slow (0.45 keV/u) multiply charged Ar ions from an atomically clean and flat LiF(001) surface. By relating projectile energy loss to kinetic electron emission we were able to determine contributions from potential electron emission even in the presence of a considerable number of kinetically excited electrons. Our results suggest a practically complete use of the available potential energy for electron emission during grazing scattering in sharp contrast to findings for the normal incidence case.

Path-dependent neutralization of multiply charged Ar ions incident on Au(110).

Using a time-of-flight technique we have investigated the backscattering of 5 keV Ar(2+) and Ar(11+) projectiles from Au(110). A strong dependence on target azimuth is found for the neutral flux resulting from (quasi)binary projectile collisions with target atoms, while for the charged components only a weak dependence is seen. A deconvolution of the observed dependences based on trajectory simulations clearly shows site-specific neutralization differences between the various possible binary collisions occurring with surface atoms. Such differences must be properly accounted for in order to permit meaningful comparison with theory.

Measurements of soft X-rays in collision of slow multiply charged Ar ions with an amorphous C target

Soft X-rays were measured in collision of 1–3 keV/u Ar q+ ( q=2–14) ions on an amorphous C target. Ar L X-rays due to initial L-shell holes were successfully decomposed. It was found that L-shell vacancies of Ar were filled stepwise primarily via 3s–2p transition for each step.

L X-ray emission from slow multiply charged Ar ions bombarding Be and Al targets

Projectile L X-rays are observed for 18–260 keV Ar q+ ions ( q =7 − 14) bombarding Be and Al targets. X-ray yields are found to increase with the L-shell hole number for q ≥ 9. The X-rays are shown to be emitted stepwise, which allows to disintegrate the spectra into the individual steps. It is found that 3s-2p transition is dominant in each step. Transitions from higher angular momentum states like 3d-2p and those from higher principal quantum numbers are relatively weak.

Desorption induced by electronic potential energy of multiply charged ions

Particle desorption is investigated in terms of bombardment of a GaAs surface by slow multiply charged Ar ions (charge state q ⩽ 9, kinetic energy E k ⩽ 3 keV). The desorption yield of Ga and As atoms as well as H + ions drastically increased with the charge state of the incident Ar ions, but was changed little by the kinetic energy of the Ar ions. These results demonstrate that desorption reactions at the surface are greatly enhanced by the potential energy of the incident ions. From an analysis of the potential energy dependence of the desorption yield based on the Coulomb explosion model, it is found that the lifetime of multiple holes created by the multiply charged Ar ions is longer than that of a single hole by 2 to 3 orders of magnitude.

Desorption of Ga and As Atoms from GaAs Surface Induced by Slow Multiply Charged Ar Ions

A reaction on a semiconductor surface induced by the potential energy of slow multiply charged ions (MCIs) has been investigated. By using an Einzel-type ion decelerator, beams of slow MCIs ( Arq +; q≤10) with an ion current of several tens of nanoamperes and with the kinetic energy (E k) of 30×q eV were produced. Irradiating a GaAs surface with the slow Arq + induced the desorption of Ga and As atoms, and this desorption was almost independent of the E k but strongly dependent on the q; that is, on the potential energy (E p) of the Arq +. The effect of E p on atom desorption was analyzed quantitatively in terms of a model based on the Coulomb repulsion between holes generated on the surface through neutralization of the MCIs.

Light emission from a Ag target bombarded by multiply-charged Ar ions

Light emitted by Ag atoms following the bombardment of a Ag target with Ar ions has been studied. Light yields that include contributions from both displaced surface and sputtered atoms have been obtained as a function of incident ion beam kinetic energy and with different Ar ion charge states. No change in the light yield was observed as the incident ion charge state was varied. The light yield was found to increase by nearly a factor of 10 as the ion beam kinetic energy changed from 8 to 100 keV.

Light emission from Na atoms sputtered by multiply-charged Ar ions

Light emitted by Na atoms, following the bombardment of a NaCl target with multiple-charged argon ions at 48 keV, has been studied for charge states 4 +, 8 + and 12 +. The yield of the unresolved Na D lines was observed as a function of the distance from the target surface and the intensity of the beam as well as the charge state of the incoming ion. The yield of the sputtered Na atoms varied linearly with the beam intensity but was independent of the charge state of the Ar ion. The light yield from the surface of the target increased with the charge state of the Ar ion.

New microwave ion source for multiply charged ion beam production

To obtain high-current beams of rather lower-charge-state multiply charged ions, a new microwave ion source is designed. Ion beams of a few mA are extracted from the plasma and mass-analysed. The extracted beams have large quantities of multiply charged Ar ions at relatively lower gas pressures of 10 −4−10 −3 Pa. In addition, these quantities tend to effectively increase with microwave power. The microwave power necessary for mA-class implantation current of low-charge-state ions is estimated to be from 3–5 kW.

Charge State Distribution Measurement in an ECR-Discharge by VUV-Spectroscopy

The charge state distribution of multiply charged Ar ions in an electron cyclotron resonance (ECR) heated microwave discharge (Bernhardi et al. 1976) was measured by means of VUV-spectroscopy in the wavelength region λ ≤ 100 nm (Marlinghaus 1984). Ion densities were computed from absolute line intensities in a modified corona model. Assuming electron impact excitation of groundstate ions to play the major role and neglecting all other processes leading to excitation, the ion density nz is given by