X-ray induced ion desorption from transition metal oxalates

Mass-spectrometric analysis of a number of atomic, molecular and double-charged ions desorbed from the surface of Mn, Co, Ni and Cu oxalate hydrates under Mg K alpha X-ray irradiation was performed. The yield of desorbed ion species was found to steadily increase across the series of oxalates from MnC2O4 center dot 2H(2)O to CuC2O4 center dot xH(2)O, exhibiting an inverse dependence on the -OCO-Me-OCO- bonds strength. Analysis of X-ray induced ion desorption from the surface of CoC2O4 center dot 2H(2)O annealed at different temperatures was demonstrated to be useful in studying compositional and structural alterations occurring in the topmost surface layer of the oxalate during the process of its thermal decomposition. The temperature dependences of the yield of characteristic ions were shown to be capable of discerning the dehydration and decomposition stages in this process. The probability of desorption and survival of different ions exhibited different dependence on the bonding and structural characteristics of the oxalates. The obtained results are compared with data provided by TG/DTA coupled with mass spectrometry and XPS techniques. Possible mechanisms of X-ray induced ion desorption from oxalates are discussed.