M. Meron

Phobis, a photon beam ion source for production of highly-charged ions☆

Abstract An ion source based on successive photoionization of trapped ions is now possible using high-brightness X rays from a modern synchrotron storage ring. Calculations based on the design parameters for the National Synchrotron Light Source at Brookhaven indicate that degrees of ionization and beam intensities should be comparable to those achieved with existing EBIS, ECRIS, or recoil-ion sources.

On the 3s-3p and 3p-3d Transitions in Ne-like Ni XIX

An experimental and theoretical study has been made of the 3s-3p and 3p-3d transitions in Ni XIX. The method of beam-foil spectroscopy, using 30-64 MeV Ni ions from a tandem accelerator, has been combined with theoretical calculations using the multiconfiguration Dirac-Fock (MCDF) program.

Synchrotron radiation production and trapping of highly charged ions

Abstract Wiggler-enhanced synchrotron radiation will soon be available at dedicated facilities such as the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory. Two recent proposals to study highly-charged ions produced by successive photoionization with broad-band synchrotron radiation are based on the design parameters of the NSLS X-ray ring. Previous calculations indicated that in a suitable Kingdon trap, concentrations of 5 × 107 Ar18+ ions per cm can be attained in a few seconds trapping time and that in a Penning trap 5 × 103 Ar17+ ions could be stored at near thermal energies (300 K) to study, for example, charge transfer collision processes for cold, highly-charged ions. Here the previous work is reviewed and the earlier calculations are extended. The addition of an axial magnetic field to a Kingdon trap is shown to improve expected PHOBIS performance.

X-ray spectroscopy of Cl-Ar quasi-molecular orbitals from 1sσ-2pπ transitions

The quasimolecular 1sσ-2pπ transition energy as function of the internuclear distance is obtained for the first time in a direct way from the interference structure observed in quasimolecularK x-ray spectra from low energy (2.5, 5, 10 and 20 MeV) Cl16+ on Ar collisions at fixed impact parameter. The experimental results are in fair agreement with quasimolecular transition energies calculated with a two-center potential.

Atomic physics and synchrotron radiation: The production and accumulation of highly charged ions

Abstract Synchrotron radiation can be used to produce highly-charged ions, and to study photoexcitation and photoionization for ions of virtually any element in the periodic table. To date, with few exceptions, atomic physics studies have been limited to rare gases and a few metal vapors, and to photoexcitation energies in the VUV region of the electromagnetic spectrum. These limitations can now be overcome using photons produced by high-brightness synchrotron storage rings, such as the X-ray ring at the National Synchrotron Light Source (NSLS) at Brookhaven. Furthermore, calculations indicate that irradiation of an ion trap with an intense energetic photon beam will result in a viable source of highly-charged ions that can be given the name PHOBIS: the photon beam ion source. Promising results, which encourage the wider systematic use of synchrotron radiation in atomic physics research, have been obtained in recent experiments on VUV photoemission and the production and storage of multiply-charged ions. An overview of the field, current plans, and future possibilities will be presented.

Charge state evolution in an ion trap irradiated by VUV synchrotron radiation

Abstract The energies of photons obtainable from the VUV ring at the National Synchrotron Light Source (NSLS) are ideally suited for high-efficiency ionization of atomic-shell electrons. Given the high fluxes of photons available on a wiggler beam line, multiple photoionization in an ion trap can be easily achieved within times short compared to typical ion storage times in the trap. Measurements of the time evolution of ion population in such a trap can yield ionic photoionization cross sections and charge-exchange interaction rates for ion-atom or ion-ion collisions. The various processes governing this time evolution are discussed and model calculations illustrating the relative importance of these processes under different conditions are presented.

Experiments With Highly Ionized Low-Energy Tandem Accel-Decel Beams

The present status of the production of low-energy highly ionized beams by the 4-stage tandem accel-decel method is surveyed, and their use in three atomic physics experiments is summarized. The experiments are: the measurement of the charge state dependence of K-X-ray production in S+q-Ar collisions at 10 MeV, the impact-parameter dependence of quasimolecular X-rays in S+15-Ar collisions again at 10 MeV, and the determination of charge transfer cross section in S+q + Ar, He collisions. The results of the three experiments give evidence that the 4-stage accel-decel ion production technique is extremely powerful and useful.

Design considerations for a combined synchrotron-light source and heavy-ion storage ring Atomic Physics Facility

Abstract An atomic physics facility (APF) based on the combination of photons produced by a synchrotron light source with heavy ions in a storage ring will open the way to the study of ionic states of almost all elements. The design considerations for such a facility are discussed in terms of the use of synchrotron radiation for photoexcitation and ionization experiments. Design considerations for an APF are given in terms of the accelerator facilities presently available at BNL which include the National Synchrotron Light Source and Tandem Van de Graaff Laboratory. The results show that the concept is valid and therefore that implementation would result in entirely new capabilities for the study of multiply-ionized atoms.

Synchrotron radiation inner-shell photoionization of atomic and molecular gases

Abstract A time-of-flight (TOF) spectrometer has been used to measure the average kinetic energies of near-thermal atomic and molecular ions, as well as energetic molecular ion fragments, produced by inner-shell photoionization of atomic and molecular gas targets using X-rays from the National Synchrotron Light Source (NSLS). While atomic and molecular ions acquire very little energy from the initial photoionization event and subsequent vacancy cascades, multiply-charged molecular ions decompose rapidly, producing fragment ions which have kinetic energies determined by their configuration at the moment of decomposition. The strong effects observed suggest that this technique may be extended to the study of configurations of free molecules as well as the orientation of molecules adsorbed on surfaces.

Investigations of molecular orbitals with accel-decel beams

Abstract Quasimolecular transition energies can be found directly from the impact-parameter dependence of interference structure observed in measured K X-ray spectra. As these experiments require a K-vacancy bearing projectile at collision velocities small compared to the equivalent K-shell electron velocity, the accel-decel technique has to be used. Such an experiment was performed at the BNL Tandem Accel-Decel Facility for collisions of Cl 16+ with Ar at energies ranging from 2.5 to 20 MeV. A new method of analysis using the uniform asymptotic approximation is described here. Quasimolecular transition energies derived using this method are compared to results of a previous analysis based on the determination of the relative positions of maxima and minima in the interference patterns.