Tom J. Gray

Cross sections for K-shell ionization, x-ray production, or auger-electron production by ion impact

Abstract Cross sections for K x-ray production, K Auger-electron production, and K -shell ionization are tabulated as functions of target and projectile atomic numbers and projectile energy. The data are given in two tables. Table I presents data for the target-projectile systems where Z 1 Z 2 ≲ 0.3 . Table II presents data for published results where no restriction on the ratio Z 1 Z 2 is applied and the studies were reported including data for different charge states of the incident heavy ion. Data are included in both tables for heavy ions incident upon gaseous targets, thick solid targets, and thin solid targets. However, data for solid targets ( Z 1 Z 2 > 0.3 ) that have not taken into account the effects of target thickness on measured target x-ray yields are not included in the present tabulations. The literature from 1973 through 1977, has been covered. This work is thus a sequel to the 1973 compilation of Rutledge and Watson .

Low divergence low energy recoil ion source

Abstract We report test results for a recoil ion source that was developed at the J.R. Macdonald Laboratory. This new source has the advantage of producing an essentially parallel beam of low energy highly charged recoil molecular and atomic ions with a high ion extraction efficiency. We measured recoil beams of various energies (50–900 eV/ q ). The beam diameter was determined to be approximately 2 mm with a divergence of 5 mrad. The extraction efficiency for recoil ions produced in the source was approximately 30%. The recoil ion source was also operated in a pulsed mode by applying a 100 ns 40 V pulse to provide the extraction field for the recoils. The source was pumped by a 1 MeV/amu F 4+ dc beams. Using this technique we measured pulsed recoil ion beams of Ne q + ( q = 2–5), Ar q + ( q = 3–8), He + and He 2+ .

Surface Spectroscopy Using High Energy Heavy Ions

Surface atoms ionized by high energy heavy ions have been detected by time-of-flight and quadrupole mass spectroscopic techniques. The experimental arrangements are described and potential applications are suggested. Both techniques are demonstrated to produce significant improvements in the detection of atomic hydrogen, with the TOF method producing a nine order of magnitude increase in the sensitivity of atomic hydrogen compared to standard nuclear analysis methods.

A Review of Recoil Ion Physics

A review of recoil ion physics is presented. A brief history on the subject is introduced. The production of low velocity highly-charged recoil ions by fast heavy ion beams is discussed. Experiments which utilize the LEHQ beams to measure charge exchange cross sections and energy gain spectroscopy are discussed.

A Study of Transfer Excitation in F8+ + He, Ne and Ar Collisions

High resolution x-ray spectroscopy has been used to measure F K x rays resulting from the decay of doubly excited two electron states formed during F8+ + He, Ne, or Ar collisions. The energy range spanned by the spectrometer includes the 2s2p(3P) ¿ 1s2s(3S), 2s2p(1P) ¿ 1s2s(lS), 2p2(1D) ¿ 1s2p(1P), 2p2(3P) ¿ 1s2p(3P) and the 2p2(1S) ¿ 1s2p(1P) transitions. These states may be formed by nonresonant transfer excitation, in which electron excitation is coupled with electron capture to an excited state, or by resonant transfer excitation, a process related to dielectronic recombination, in which the capture of a loosely bound target electron results in projectile electron excitation. Calculations have been performed to estimate the contribution of each process to the total measured cross section.

Capture by Highly-Charged Low-Energy Ions Studied with a Secondary Ion Recoil Source

When a highly-charged fast projectile collides with a neutral atom in a gaseous target it may, in a single collision, remove many electrons from the target while transferring no more than a few eV to the targets center of mass. These low-energy highly-charged (LEHQ) recoils may be extracted for use as a secondary ion beam to study subsequent capture reactions in a second gas target. We have developed a LEHQ ion source based on this principle, pumped by 1-2 MeV/amu beams of F, S and Cl. In this paper we discuss 1) the properties of the ion source, and 2) cross sections measured with the source for single and multiple electron capture by Ar+q from Ne for 2 < q < 10 and Ar energies between 200 and 1000 eV per q.

Formation of N and N2 recoil ions from the bombardment of N2 gas by a 19 MeV F4+ beam

Abstract Absolute total cross-sections are reported for the collisional production of highly charged low-velocity nitrogen recoil ions produced from the bombardment of N 2 gas by a 19 MeV F 4+ beam. The formation of these low-velocity recoil ions of the form N 2 α + ( α =1–4) and N β + ( β =1–3) have been observed at a recoil-ion kinetic energy of 834.4 eV and at N 2 gas-target pressures between 0.6 and 4.2 mTorr. The identification of these low-velocity recoil ions is established based upon the calibration of their time-of-flight.

Fragmentation of CH4 in collisions with fast highly charged ions

Measurements of the production cross sections for singly charged molecular ions by high energy (1 MeV/amu) Fq+ (q=4,6–9), Siq+ (q=5,6,8–12), and Cq+ (q=3–6) projectiles incident on a CH4 target are reported. Similar measurements for singly charged recoil ions are presented for H+ (E=1–11 MeV) projectiles incident on CH4. We observed good agreement between our proton results and earlier electron measurements. Theoretical calculations for the sum of the cross sections for production of all singly ionized CHn fragments from CH4 are presented using the Born and Glauber approximations, and both calculated cross sections are in reasonable agreement with the measured cross sections. Production of CH+3, CH+2, CH+, and C+ fragments is analyzed both as a function of projectile charge and projectile velocity. Deviation from quasiequilibrium theory is observed in the relatively small cross section ratios of C+ and CH+ to CH+4 as a function of projectile charge.

Status of the Kansas State University superconducting linac project

Funding for the construction of the superconducting linac at Kansas State University was approved by the Department of Energy on May 15, 1985. The project is funded out of the Division of Chemical Sciences, USDOE. Initial design and staff technical training was initiated during 1984–85 with laboratory personnel working at both Florida State University and Argonne National Laboratory. The linac under construction is based upon the Nb split‐ring resonator technology developed at Argonne National Laboratory for ATLAS. The linac at Kansas State University will have 14 superconducting resonators with nine low‐β (β=0.06) and five high‐β (β=0.105) units operating at 97 MHz. Work has progressed on both of the single‐resonator cryostats for time bunching and energy rebunching, respectively, with the major cryostat components presently under construction by C. E. Raymond Enterprise Manufacturing, a division of Combustion Engineering, with scheduled delivery of the single resonator cryostat vacuum housings, LN2‐cool...

Molecular ion collision chemistry using particle accelerators

Abstract A spectroscopy for molecular ions is reported which is based upon the two-dimensional analysis of the time of flight and the ions final state using a dispersive electrostatic analyzer. These ions are produced in a recoil ion source by a pulsed fast F4+ pump beam. Two-dimensional recoil ion spectra for CH4 source gas at pressures of 0.5 mTorr and 4.0 mTorr are reported. Model calculations for spectral distributions provide the identifications of various processes involving specified molecular ion species. The first direct observations of metastable CH[su2+], CH32+, CH43+, and CH23+ molecular ions are reported and limits on the lifetimes for these ion species are deduced.