Secondary ion emission of phenylalanine as function of primary ion charge

Abstract

At the heavy ion accelerator UNILAC/GSI-Darmstadt Phenylalanine films of 2000 Å thickness evaporated onto Al-foils were irradiated by ¹⁶N and ²³⁸U ions having a fixed energy of 1.4 MeV/N. The yields of secondary ions ejected from the target surface were investigated as function of the primary ion charge q. Changing the charge state q/e from 2⁺ to 49⁺ an increase of ion yields is observed, which does not follow a straight qⁿ-dependence. The same targets were also irradiated by ⁴He²⁺ions of 1.37 MeV/N. The corresponding ion yields were 430 times lower than yields measured with ¹⁴Ne². Additionally the mass spectra obtained with heavy ions were compared with laser induced ion desorption. It turned out that the relative yields of laser ejected ions are very sensitive to the amount of energy absorbed in the target. - The results are discussed in the frame work of the modified lattice potential model of Watson and Tombrello (ref.1).