G. Sampoll

Recoil-ion kinetic energies for 96 MeV Ar collisions

Abstract The kinetic energies of He, Ne, and Ar recoil-ions produced in single collisions with 96 MeV Ar 4+ and Ar 15+ projectiles have been determined from high resolution time-of-flight measurements. They were found to vary from the ambient thermal energy for charge 1 recoil-ions to 5 eV for Ar 11+ recoil-ions. Average impact parameters were deduced from these results.

Two-fragment coincidence studies of molecular coulomb explosions induced by heavy ion impact

Abstract Time-of-flight (TOF) spectroscopy was used to study the ionic species produced in collisions of 40 MeV Ar13+ with molecular oxygen. Ions from the dissociation of molecular ions having charges as high as 10 + were observed. The flight times of the first ion and the difference in flight times between the first and second ions of binary dissociation events were recorded event-by-event, thereby retaining their correlation. Off-line sorting of the data provided TOF and time difference spectra containing well resolved peaks associated with each of the charge division pairs produced in the dissociation process.

Multiple ionization of He, Ne, and Ar by high velocity N7+ ions

The yields of He, Ne, and Ar recoil ions produced in collisions with 10–40 MeV/amu N7+ projectiles were measured by the time-of-flight technique. The ratio of the yields for double and single ionization of He and Ne were found to be higher than predicted by theoretical and semiempirical calculations. The role of electron correlation in multiple ionization was assessed by comparing the experimental data for Ne and Ar with the results of an independent electron approximation analysis.

Ionization of noble gas atoms by alpha particles and fission fragments from the decay of 252Cf1

Abstract Charge state distributions of He, Ne, Ar, Kr, and Xe ions produced in single collisions with alpha particles and fission fragments from the decay of 252 Cf have been measured using time of flight spectrometry. The measurements reveal that the maximum number of electrons removed in a fission fragment collision ranges from eight in the case of Ne to 20 in the case of Xe. Recoil-ion production cross sections have been determined for the resolvable ionic charge states and compared with the predictions of a model based upon the independent electron approximation.

K- plus L-shell ionization of fourth row elements by 30 MeV/amu Ar ions

Abstract Spectra of K X-rays produced by collisions of 30 MeV/amu Ar ions with metallic targets of Ti, V, Cr, Fe, Co, Ni, Cu, and Zn were measured with a Si(Li) detector system. The measured Kα and Kβ transition energies were compared to the results of Dirac-Fock calculations to estimate the average number of L-shell vacancies at the time of K X-ray emission. The target double-to-single K-shell ionization probabilities were also determined, along with the relative probabilities of having single and double K-shell vacancies in the projectile during passage through the metal foils.

Cross sections for Ar recoil ion production by 1 MeV/amu Oq+ (q = 2–8)

Abstract Cross sections for the production of recoil ions of Ar 1+ through Ar 10+ in collisions with 1 MeV/amu O 2+ through O 8+ ions have been measured using the time-of-flight (TOP) method. Postcollision charge state analysis of the projectile was performed to distinguish between events involving pure ionization ( q = 2–8), one-electron loss ( q = 2–6), two-electron loss ( q = 2–4), one-electron capture ( q = 3–8) and two-electron capture ( q = 5–8). The total direct ionization cross section was found to increase as q 1.5 . The electron capture cross sections also increased as a function of q , while at the same time the cross sections for electron loss decreased. Both of these processes exhibit a steeper q dependence than the pure ionization process. The charge state distributions are bell shaped for the electron capture process and for the electron loss process at high q . For electron loss at low q the distributions are similar to those for the pure ionization process.