Fast atom bombardment and secondary ion mass spectra of iodonium salts: Interpretation of spectra and implications for sputtering mechanisms

Abstract

Positive ion fast atom bombardment and liquid secondary ion mass spectra of aryl iodonium salts usually contain the intact cation as the base peak in the spectrum, along with lower abundance fragment ions that result from cleavages, rearrangements, and in some cases, combinations of such losses with addition of hydrogen from the matrix. An interesting rearrangement that leads to loss of the central iodine as a neutral atom occurs in source fragmentations as well as in low collision energy collision-activated dissociation. Energy-resolved tandem mass spectrometry is used to establish the relative facilities of the rearrangement and cleavage reactions of the intact cation. Tandem mass spectrometry is also used to identify reduced forms of the intact cation and its fragments. The occurrence of these reactions implicates direct fragmentation in the condensed phase or in a solvent-salt cluster in the selvedge immediately above the sample surface.