Description: This article discusses simultaneous measurement of the average ion-induced electron emission yield and the mean charge for isotachic ions in carbon foils. Knowledge of the incident ion's atomic number (Z₁) dependence of ion-induced electron emission yields can be the basis for a general understanding of ion-atom interaction phenomena and, in particular, for the design of Z₁-sensitive detectors that could be useful, for example, in the separation of isobars in accelerator mass spectrometry. The Z₁ dependence of ion-induced electron emission yields, y, has been investigating using heavy ions C³⁺, O³⁺, F³⁺, Na³⁺, Al³⁺, Si³⁺, P³⁺, S³⁺, Cl³⁺, K³⁺, Ti³⁺, Cr³⁺, Mn⁴⁺, Fe⁴⁺, Co⁴⁺, Ni⁴⁺, Cu⁴⁺, Ga⁴⁺, As⁵⁺, Br⁵⁺, Ru⁷⁺, Ag⁷⁺, Sn⁷⁺, and I⁸⁺ of identical velocity (v = 2v₀, where v₀ is the Bohr velocity) normally incident on 50 μg/cm² sputter-cleaned carbon foils. Measured yields as a function of Z₁ reveal an oscillatory behavior with pronounced maxima and minima. Contrary to previously reported yields that assumed to monotonically increasing empirical mean charge state for the exiting ion, the present work indicates the Z₁ oscillations in the experimentally measured yields, a fact masked in previous work. The strong Z₁ oscillations can only be observed by simultaneous measurement of the yield and the ...

Description: This article discusses experimental evidence for a discrete transition to channeling for 1.0-MeV protons in Si〈100〉. Abstract: The present work reports the experimental evidence of anomalies exhibited by the energy loss and energy straggling of channeled protons in silicon in transmission measurements versus the incident angle. Results are presented for 1.0-MeV protons channeled along the 〈100〉 axis for a silicon foil of 3.8 μm thickness. It is shown that the transition from random to a channeling condition is discrete. The energy spectra of transmitted ions show a random peak (lower energy) and a channeled peak (higher energy). The random peak has a fixed energy, while the energy of the channeled peak increases as the target crystal's axis approaches alignment with the direction of the incident ion beam. The results support a model suggesting that the channeled ions lose energy only to valence electrons and are concentrated in a narrow cone about the direction of incidence when they emerge from the crystal. The energy straggling of channeled particles reaches a minimum in the hyper-channeled condition. Both the energy loss and the energy straggling of channeled protons show a dependence on the local electron density.