J. A. Biggerstaff

Resonant-coherent excitation of channeled ions.

A first-principles calculation of the resonant-coherent excitation of planar-channeled hydrogenic ions is presented. The interplay between coherent interaction with the periodic crystal lattice potential and inelastic electron-electron collisions is shown to be crucial in both intraionic transitions and electron loss from the ion. The magnitude of resonant-coherent excitation is predicted to oscillate with the amplitude of the oscillations of the ion trajectory. Good agreement is found with experiments.

Resonant coherent excitation of O7+, F8+, and C5+ in the 〈100〉 axial channel in gold

Abstract Previous studies have shown that when an ion moves in an axial channel with a velocity, v , such that hKv/ d = ΔE ij , transitions are coherently induced. K is an integer, d is the longitudinal atomic spacing in the channel, and ΔE ij , is an ionic transition energy. Since the ionization cross section for an excited state is much greater than that for the ground state, the effect for 1s → 2p transitions is observed as a minimum in the surviving, one-electron charge-state fraction as the velocity is scanned through a resonance. Resonant coherent excitation (RCE) for the following one-electron ions, moving in the 〈100〉 axial channel in gold, are reported here: O 7+ , K = 2, 85.9 MeV; F 8+ , K = 2, 163.6 MeV; and C 5+ , K = 1, 81.6 MeV. The K = 2 resonances have a single narrow dip superimposed on a broad minimum, in contrast to the doublet minimum previously observed for lower Z ions. Comparison is made to predictions based on the positions of the Stark components deduced from the rainbow scattering theory. A similar comparison is made for the stronger and broader K = 1 resonance of C 5+ .

Proton particle-hole states in116Sn

Abstract The reaction115In(3He,d)116Sn has been studied at 25.6 MeV. It is found that low-lying neutron particle-hole states are extremely weakly excited whereas core excitations consisting of the g 9/2 proton hole coupled to protons in the d 5/2, d 3/2 and g 7/2 shells are strongly excited. DWBA estimates of the strength of the various “gross structure transitions” are given.

Isobaric spin dependence in proton transfer reactions

Abstract Results of an experimental investigation of 54Fe(d, n)55Co reaction are presented and spectroscopic strengths for both T states are derived. It is concluded that within the limits of experimental and analytical uncertainties there is no discrepancy between the spectroscopic factors for T> analogue states as derived from the (d, n) and (3He, d) reactions.

The Velocity Dependence of the Stopping Power of Channeled Iodine Ions from 0.6_MeV to 60_MeV

Abstract Electronic stopping powers of heavy particles in the low-velocity region (below the velocity for the stopping power maximum) have been assumed to be strictly velocity-proportional 1 ). The theoretical estimates of Lindhard, Scharff and Schiott 2 ) and Firsov 3 ) have been used, with certain scale adjustments, whenever stopping powers or ranges are required, especially for cases where direct measurements are not available. Recent data suggest that this procedure will cause serious errors in range estimates for heavy ions.

Radiative Electron Capture by Channeled Oxygen Ions

Recently Schnopper et al. [1] reported a new feature in the x-ray spectra observed when solid targets were bombarded with energetic, highly-stripped heavy ions. They observed a broad x-ray band well above the highest energy characteristic x-ray line from the projectile. This new feature was identified as radiative electron capture (REG). The phenomenon of REC becomes most probable when the incident heavy ions are completely stripped, and no outer shell electrons are available to fill K-shell vacancies. Then a free or weakly bound target electron can be captured directly into the K-shell of the moving ion, emitting a photon. The energy of a REC photon resulting from the capture of a free electron by an ion of charge Z, mass M, and energy E, is given by the expression:

Charge State Dependence of Si K X-Ray Production in Solid and Gaseous Targets by 40 MeV Oxygen Ion Impact

{{\text{E}}_{\text{p}}} = {{\text{Z}}^{2\,}}\,{\text{Ry}}\,\,{\text{ + }}\,\frac{{{{\text{M}}_{\text{e}}}}}{{\text{M}}}\,\,{\text{E}}

Charge State Dependence of Stopping Power for Oxygen Ions Channeled in Silver

(1) where Ry is the Rydberg energy and Me the electron mass. The first term is the binding energy of an electron in the hydrogen-like ion and the second the energy of an electron moving at a velocity equivalent to that of the ion. As noted by Schnopper [1],the actual width of the observed REC line is affected by a number of things. In measurements utilizing heavy ion beams incident on amorphous solids, the heavy ions will have a distribution of charge states inside the solids and each charge state can result in a REC photon of a different energy as can be seen from eq. (1).