B. Sulik

Identification and angular distribution of the KL-LL2,3L2,3 satellites in the Ne K Auger spectra from the 5.5 MeV u-1 Ne3+-Ne collision process

The angular distributions of the KL-LL2,3L2,3 satellite transitions were measured in the 5.5 MeV u-1 Ne-Ne collision. A definite non-isotropic angular distribution was found for the satellite transitions 125pp(3P-2P), 125pp(1P-2P) and 125pp(1P-2D), as well as for the sum of the 125pp(3P-2D) and 116(3S-2D) transitions, while an isotropic angular distribution was found to characterise the 116pp(1S-2D) transition.

Guided transmission of 3 keV Ne7+ ions through nanocapillaries etched in a PET polymer

Abstract We measured the transmission of 3 keV Ne 7+ ions through capillaries of 100 nm diameter and 10 μm length produced by etching ion tracks in a polyethylene terephthalate polymer foil. The foils were tilted up to ±25° for which the incident ions are forced to interact with the capillary surface. The majority of Ne 7+ ions were found to survive the transmission in their initial charge state. For tilted foils the angular distributions of the transmitted particles indicate propagation of the Ne 7+ ions parallel to the capillary axis. This capillary guiding of the Ne 7+ ion provides evidence that part of the ions deposit charges within the capillaries in a self-organizing process so that a considerable fraction of the ions is transmitted through the capillaries. A non-linear model is introduced to describe the essential features of the capillary guiding.

Guided transmission of slow Ne6+ ions through the nanochannels of highly ordered anodic alumina

A highly ordered hexagonally close-packed nanochannels array was prepared using the self-ordering phenomena during a two-step anodization process of a high purity aluminium foil. The anodized aluminium oxide, with pore diameters of about 280 nm and interpore distances of about 450 nm was prepared as a suspended membrane of about 15 mu m thickness on the aluminium frame to which it belongs. The Al2O3 capillaries were bombarded with 3 keV Ne6+ ions. The first results unambiguously show the existence of ion guiding observed at 5 degrees and 7.5 degrees tilt angles of the capillaries compared to the beam direction. To the best of our knowledge, such ion guiding effects of slow ions through hexagonally ordered nanochannels in alumina has not been reported previously.

A spherical mirror-double cylindrical mirror electron spectrometer for simultaneous energy and angular distribution measurements: design, construction and experiences

Abstract The design and construction of a triple-stage electrostatic electron spectrometer are described together with the experiences obtained during the utilization of the equipment in high energy ion-atom collision experiments. The spectrometer (called ESA-21) consists of a spherical (first stage) and a double-pass cylindrical mirror unit. It works in a rather broad energy resolution range (from about 5×10 −4 to 6×10 −3 ) and a wide electron energy region (from 50 eV to 16 keV) with simultaneous measurement of the energy and the angular distribution (in the region from 0° to 180°) of the electrons.

A simple theoretical approach to multiple ionization and its application for 5.1 and 5.5 MeV/u Xq++ Ne collisions

The simple geometrical model we developed recently for ionization probabilities on the basis of a geometrical BEA picture is generalized and extended to take into account magnetic substates and non-zero impact parameter ion-atom collisions. Ionization probabilities per electron for the L shell and separately for the 2s and 2p Subshells of neon in 5.1 MeV/u N+ and N7+ as well as 5.5 MeV/u H+ collisions were determined from 0.8−1 eV resolution K-Auger spectra. Anisotropy parameters of KL-LL23L23 satellite lines were determined in 5.5 MeV/u Ar6+, Ne10+ and 5.1 MeV/u N2+ collisions. The comparison of the extended model with the experimental data shows a good agreement. The model seems to be able to give account of the dependence of the ionization probability on quantum numbers l and m. Comparing the results with a wide range of experimental data no contradictions were found with the universal scaling features predicted by the model. By analyzing the impact parameter dependence of ionization probabilities the validity of the model was estimated to break down at ν1 ≈ ν2/3 towards lower impact velocities.

Charge scaling of ionisation probabilities in ion-atom collisions for zero impact parameter

A simple encounter probability model is constructed for approximating the mean L-shell ionisation probability at zero impact parameter, pL(0), as used in the multiple ionisation theories of heavy-ion collisions. The model establishes a simple scaling rule for pL(0) as a function of Z1/vi which behaves asymptotically as pL(0) approximately=(Z1/vi)2 for low projectile charge Z1 and tends to unity for high Z1 values, in the high velocity limit vi>>va.

Fragmentation of H2O molecules following the interaction with slow, highly charged Ne ions

We measured the energy and angular distribution of fragment ions from collisions of 2–90 keV Neq+ ions (q = 1, 3, 5, 7 and 9) with H2O molecules. A strong dependence on the charge state of the incident ion was observed. The results are interpreted within the framework of a Coulomb explosion model. Deviations from this model in the energy and angular distribution of recoil ions are attributed to post-collision effects by the electric field of the projectile. Absolute cross sections for ion production were measured and found to be consistent with the cross sections calculated using the classical over-barrier model.

Anisotropic proton emission after fragmentation of H2O by multiply charged ions

Ion-induced fragmentation of H2O molecules was investigated experimentally by 3He^2+ impact as a function of the energy in the range from 1 to 5 keV, as well as a function of the charge state of 20 keV 20Ne^q+ projectiles (q = 3 and 7). The fragments were detected in the angular range from 25° to 135° with respect to the incident beam direction. Particular emphasis is given to protons originating from collisions at large impact parameters involving a Coulomb explosion mechanism. Absolute cross sections dσ/dΩ, differential in the emission angle, are found to be anisotropic. Protons are preferentially emitted at angles near 90°, with cross sections being ~50% larger than those at forward and backward angles. Possible mechanisms causing anisotropic emission of protons from fragmenting H2O are discussed.

Fermi-shuttle acceleration of electrons in ion–matter interaction

Abstract Large electron yields, compared to theoretical predictions, have often been observed in the high-energy part of the electron spectra in collisions of energetic ions with atomic, molecular or solid targets. The relative enhancement of the electron emission yield at high energies can be especially strong in ion–solid collisions. In this work, following a brief overview, recent experimental evidences are presented for Fermi-shuttle type accelerating electron scattering sequences in ion–atom collisions. Signatures for double (projectile–target, P–T), triple (projectile–target–projectile, P–T–P) and quadruple (P–T–P–T) scattering sequences have been found in different collision systems. Our new results indicate the presence of even higher-order scattering contributions in the collisions of few keV energy N + ions with inert gas atoms. The observations support that high-energy electrons produced by accelerating scattering sequences may play a significant role in ion–solid collisions.

Strong anisotropy in the proton emission following fragmentation of H2O molecules by impact with slow, highly charged Xenon ions

We measured the energy and angular distribution of ionic fragments produced by the interaction of 1–220 keV Xe22+ ions with water molecules. The measured distributions strongly depend on the projectile charge state and energy, as seen from the comparison of the results with previously published data for 5 keV He2+, and 2 and 90 keV Ne(3–9)+ ions. A significant forward–backward asymmetry of the energy and intensity of the H+ fragments is observed. The interpretation of the experimental results is guided by means of classical trajectory simulations based on a Coulomb explosion model. The experimental finding of a strong enhancement of the H+ yield at 90° is attributed to an alignment of the molecular axis during the collision and the momentum transfer from the slow projectile.