Scanning Microscopy


After emphasizing the role of local energy deposition as a common feature of many microanalytical techniques we focus our attention to laser ionization processes in mass spectrometry of solids. Enhancement of ionization in the case of high power density laser pulses can be rationalized in terms of hydrodynamic equations. The mechanism of shock wave generation and plasma ignition as well as excess energy absorption is demonstrated. Model calculations show that a one component - one dimensional (1C-1D) description can account for such important features of the laser ionization process as energy distribution of the produced ions. The role of classical absorption in the determination of plasma formation threshold is unfolded. Present efforts to relate the results with the fine structure of mass spectra are outlined. Targets are most commonly strongly inhomogeneous in practical microprobing. The induced plasma ignition concept is introduced in order to describe poorly reproducible mass spectra in these situations.

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