P. Dück

Heavy ion induced desorption of organic compounds

Abstract The desorption of organic compounds has been studied using 16 O and 32 S ions as primary ion beam in the energy range from 8 to 40 MeV. The observed mass spectra are comparable to those obtained by bombardment with heavier ions at higher energies ( 252 Cf-fission products). Using the amino acid valine as sample the energy distributions and the yield of desorbed ions like H + , Na + , [valine+H] + and [valine-COOH] + were measured as a function of the stopping power in the sample, which is also called linear energy transfer (LET). For increasing LET the secondary ion yield increases too, but the ratio of the yields of different ions desorbed from the same surface remains unchanged. There are indications that only a certain portion of the LET contributes to the desorption process. The ratio of that portion to the total LET (as calculated by the Bragg rule) seems to be an universal function of ζ = ν ν 0 Z , where ν is the velocity of the primary ion and ν 0 Z is the Bohr velocity of a K-electron of the primary ion.

Secondary ion emission from dielectric films as a function of primary ion velocity

Abstract Secondary ion emission from (CsCl + RbBr) and Valine films irradiated by 16O and 32S ions has been studied as a function of the primary ion velocity. By means of a two fold time-of-flight technique mass spectra of secondary ions were measured simultaneously for primary ion velocities between 0.05 and 1.2 cm/ns. The yield functions show two branches, one below 0.2 cm/ns and one above, which are probably related to the nuclear and electronic energy loss, respectively, of the primary ions. A general agreement with available desorption models is not apparent.

Energy dependence of fast heavy ion induced desorption of secondary ions

Abstract Yields for positive and negative secondary ions desorbed by 12C, 160 and 32S ions with velocities ν≳109cm s 1 and equilibrium charge state distributions have been measured. The data show that the yields depend on the charge and the velocity of the primary ions and the secondary ion species. They are independent of the primary ion mass.

Experimental investigations of fast heavy ion induced desorption

Abstract Yields of secondary ions desorbed by energetic (1 MeV/amu) heavy ions from different solid samples have been measured as a function of the primary ion energy. The results are compared with predictions of models for the desorption mechanism.

Simple method for yield measurements of secondary ions desorbed by fast heavy ions of variable energy

Abstract A new method for yield measurements of secondary ions desorbed by fast heavy ions is presented which reduces the data collecting time in cases where the energy dependence of the yield on the primary ion energy is of interest. The method allows yield measurements to be carried out at accelerators with fixed energy.

Yield measurements of organic molecules desorbed by energetic heavy ions as a function of the ionic charge state

Abstract Energetic 16 O ions having different well defined charge states at one particular incident energy have been used to bombard the surface of a Valine sample. The experiments were performed at two different incident energies, 20 MeV and 25 MeV. The yield of the desorbed secondary ions [Valine+H] + , [Valine+Na] + , and [Valine-COOH] + has been measured. It is roughly proportional to the charge state of the primary ions and is proportional to the inverse square of the primary ion velocity.

Investigation of the reaction 14C(12C, α)22Ne for energies near the coulomb barrier

Abstract Excitation functions have been measured for the α-particle exit channel of the reaction 12 C+ 14 C at fifteen angles in the energy range E c . m . = 6.1–9.7 MeV. These excitation functions do not exhibit strong correlations which one would expect in the case of existing intermediate structure. A statistical analysis shows that the observed structures can be explained as statistical fluctuations.

Intermediate-structure resonances in the O 16 + O 16 total reaction cross section

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On the observability of “molecular resonances” in 24Mg through the 10B + 14N entrance channel

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Total reaction cross section for C 12 + C 12 in the vicinity of the Coulomb barrier

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