Laser desorption/ionization of transition metal atoms and oxides from solid argon

The oxides TiO, CrO, and CoO, formed by reaction of the laser-ablated metal atoms and O-2 in excess argon during condensation at 10 K, have been laser desorbed/ionized from solid argon with 308 nm radiation for observation by TOF mass spectrometry. Mass peaks for Ti+, Cr+, Co+, and particularly TiO+ and CrO+ were enhanced by adding to the copper support a thin film of organic acid typically used as a matrix in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Adding the C6H5Br chromophore to the Ar/O-2 gas mixture also enhanced the metal and oxide ion signals. The laser desorption/ionization (LDI) process in these cryogenic experiments with low ionization energy subject atoms and molecules is assisted by the organic acid and bromobenzene chromophores, suggesting that charge exchange plays an important role in this process.