K.W. Jones

Impact-parameter dependent K-shell ionization in ion-atom collisions. II. theory

Abstract Impact-parameter dependent differential cross sections and total cross sections for K-shell vacancy formation in ion-atom collisions are discussed in terms of promotion during collisions of electrons in random walk on ladders of level crossings to the continuum.

X-ray measurements of bremsstrahlung and electron capture by fast positive ions☆

Two broad spectral features which may be easily overlooked or misinterpreted in the discussion of X-ray spectra induced by fast atomic collisions are reported. Calculations based on relatively simple models are in good agreement with the data.

Beam-foil lifetimes of n=3 levels in Fe XIII to Fe XVI II. analysis of decay curves☆

Abstract Decay curves for spectral lines of Fe XIII–XVI were analyzed using multi-exponential and cascade-model fitting techniques. The results for lifetimes of the 2 D levels in Fe XVI, of the 1 P and 1 D levels in Fe XV, and of the 3 S level in Fe XIII agree with theoretical predictions. In sharp contrast, however, results for lifetimes of 3 P levels in Fe XV and of 2 P and 4 S levels in Fe XIV were from 1.4 to 3 times higher than theory. These discrepancies demonstrate the need for a more refined understanding of the beam-foil interaction, an increased awareness that cascade contributions are strongly dependent on atomic structure, and a determined effort to develop new prescriptions to deal effectively with the complexities of cascade analysis.

Comparison of tungsten and gold radiation from beam-foil excitation and tokamak-produced plasmas

Abstract Spectra in the 30–80 A wavelength region of tungsten and gold ions, with charge states ranging from 20–33, and 25–38, respectively, have been measured in beam-foil excitation and compared with similar spectra from tokamak-produced plasmas.

Beam-foil lifetimes of n = 3 levels in Fe XIII to Fe XVI I. Experiment using position sensitive detection

Abstract Positron-sensitive detection was used to measure the spatial decay in intensity of twelve transitions in Fe XIII to Fe XVI. A two-meter grazing incidence spectrometer was equipped with a 25 mm microchannel plate coupled to a resistive anode encoder and was positioned to simultaneously record all EUV radiation in the wavelength range from 24.5 to 31 nm. Data for foil-excited Fe ions at 35 MeV was accumulated at each of 37 foil positions until a fixed amount of beam charge had been collected in a Faraday cup. The considerable advantages of this improved beam-foil time-of-flight technique are discussed.

EUV spectra of Mo XIV to Mo XXIX

Abstract Observations of the EUV spectra of Mo XIV to Mo XXIX have been made in the wavelength region from 5 to 50 nm by foil excitation of 22 to 200 MeV Mo ion beams. The results are compared with spectra observed in tokamak plasmas and light sources and with theoretical predictions.

Impact-parameter dependence of K- and L-X-rays produced in ArAl and ArSn collisions

Abstract The impact-parameter dependence of Al and Ar K- and Sn L-X-rays produced by bombardment of solid A1 and Sn targets with 5.2 MeV argon ions has been measured. The data are compared with experimental results for gas targets and with the predictions of theoretical models.

Impact-parameter dependence of Ag K X-rays produced by bombardment of Ag BY I

Abstract The impact-parameter dependence of Ag Kα and Kβ X-rays produced by 47 and 100 MeV I ions incident on solid Ag targets has been measured. A striking difference found for the impact-parameter dependence of the Ag Kα and Kβ radiations demonstrates a variation in relative outer-shell populations which may affect the K-vacancy production mechanisms. K-vacancy production probabilities were determined from the data. The results are compared with the theoretical predictions of the molecular orbital and statistical models.

Impact-parameter dependence of inner-shell vacancy production in Ni + Mn and Ni + Pb collisions☆

Abstract The impact-parameter dependence of inner-shell vacancy production cross sections for Ni + Mn and Ni + Pb collisions have been measured at 45 MeV. Projectile Ni K-X-rays and target Mn K- and Pb L-X-rays were observed. The data are interpreted in terms of the statistical model proposed by Brandt and Jones for inner-shell vacancy formation.

Impact-parameter dependent K-shell ionization in ion-atom collisions, I. experiment

Abstract Impact-parameter dependent differential K-shell ionization cross sections for excitation by 0.7 to 2.6 MeV O, Ne and S projectiles are determined from characteristic X-ray-particle coincidence measurements on thin aluminum foils.