On the SIMS Ionization Probability of Organic Molecules.

The prospect of improved secondary ion yields for secondary ion mass spectrometry (SIMS) experiments drives innovation of new primary ion sources, instrumentation, and post-ionization techniques. The largest factor affecting secondary ion efficiency is believed to be the poor ionization probability (α) of sputtered material, a value rarely measured directly, but estimated to be in some cases as low as 10. Our lab has developed a method for the direct determination of α in a SIMS experiment using laser post-ionization (LPI) to detect neutral molecular species in the sputtered plume for an organic compound.