Molecular Colocalization Using Massive Gold Cluster Secondary Ion Mass Spectrometry.

We report on the ion emission from impacts of hypervelocity massive gold clusters for use in secondary ion mass spectrometry. Two massive gold clusters are considered, 520 keV Au4004+ and 1040 keV Au28008+. The emission of fragment ions and molecular ions is evaluated for a series of neat samples, glycine, phenylalanine, arginine, and gramicidin S. A 2 to 4-fold increase of molecular ion emission is observed from impacts of 1040 keV Au28008+ versus 520 keV Au4004+. Compared to impacts of 20 keV Ar2000+ and 20 keV (H2O)7000+ in static conditions, impacts of 1040 keV Au28008+ display a 6 to 9-fold increase in the number of detected molecular ions per projectile impact. To explain the increased emission of molecular species, we examine the size of the impact craters and calculate the ratio of molecular ions to fragment ions. The characterization of Au28008+ and the operating conditions of the gold liquid metal ion source are presented.