Quasi-discretization Of The Electron Continuum Emitted In Collisions Of 0.6 Mev U−¹ Au11+ With Noble Gases

We have measured relative doubly differential cross sections for electron emission in collisions of 0.6 MeV u−1 Au11+ projectile ions with He, Ne and Ar targets for laboratory electron-detection angles between 17\u27 and 80\u27 and electron energies from 100 eV to well above the classical binary encounter region. The authors observe that, independent of the target Zt, the electron spectra display three characteristic peak-line structures whose energies are nearly invariant with observation angle. These structures are attributed to the diffraction of quasi-free target electrons in the potential of the projectile. © 1992 IOP Publishing Ltd

Ion-beam excitation of liquid argon

The scintillation light of liquid argon has been recorded wavelength and time resolved with very good statistics in a wavelength interval ranging from 118 nm through 970 nm. Three different ion beams, protons, sulfur ions and gold ions, were used to excite liquid argon. Only minor differences were observed in the wavelength-spectra obtained with the different incident particles. Light emission in the wavelength range of the third excimer continuum was found to be strongly suppressed in the liquid phase. In time-resolved measurements, the time structure of the scintillation light can be directly attributed to wavelength in our studies, as no wavelength shifter has been used. These measurements confirm that the singlet-to-triplet intensity ratio in the second excimer continuum range is a useful parameter for particle discrimination, which can also be employed in wavelength-integrated measurements as long as the sensitivity of the detector system does not rise steeply for wavelengths longer than 190 nm. Using our values for the singlet-to-triplet ratio down to low energies deposited a discrimination threshold between incident protons and sulfur ions as low as ∼2.5 keV seems possible, which represents the principle limit for the discrimination of these two species in liquid argon

L-SUBSHELL IONIZATION PROBALITIES IN FAST ASYMMETRIC ION-ATOM COLLISIONS

It has been established that K-shell ionization probabilities in very asymmetric fast ion-atom collisions can be described well by first order perturbation theory. For the L-substates, however, impact parameter dependent ionization probabilities show severe discrepancies with these theoretical approaches. From the L-subshell ionization probabilities, the measured impact parameter dependent L111 - alignment and δ-electron emission probabilities we can deduce that the dynamical behaviour of the electron wave function during the collision has a strong influence on the measured transition probabilities

Observation Of Structures In The Binary Encounter Peak In Fast Uranium-rare Gas Collisions

For 1.4 MeV/u U33+ on rare gas atoms, the double differential cross sections Δ2σ(Ee, θ{symbol}e) ΔEeΔωe as a function of the electron emission energy Ee at different emission angles θ{symbol}e were measured. At θ{symbol}e≈40° an unexpected structure in the center of the binar encounter peak was observed, which varies strongly with the electron emission angle. © 1989

Multiple Ionization And Collision Dynamics In High-energy Uranium-rare Gas Collisions

The multiple ionization of rare gas target atoms in collisions with MeV/u highly-charged heavy ions was investigated systematically in a projectile energy (Ep) regime between 1.4 and 420 MeV/u. The absolute cross sections σ(q) for the production of Ar recoil-ions with charge state q decrease smoothly with (Ep) for q ≤ 8, whereas a distinct maximum in the Ep-dependence can be observed for higher q. Furthermore, for 1.4 MeV/u U32+ and 5.9 MeV/u U65+ impact on Ne, a new experimental technique was applied allowing the simultaneous determination of q and of the transverse (with respect to the beam axis) recoil-ion momentum pR⊥. From the good agreement of these differential absolute cross sections with the results of n-body classical trajectory Monte Carlo (nCTMC) calculations we conclude that the trajectories of the heavy nuclei are influenced considerably by the interaction with the target electrons as has been predicted by theory. © 1989