SECONDARY ION MASS-SPECTROMETRY STUDIES OF MIXED ARACHIDIC ACID AND BARIUM ARACHIDATE LANGMUIR-BLODGETT-FILMS

Bilayers of mixed arachidic acid and barium arachidate have been analyzed by secondary ion mass spectrometry (SIMS). The striking features of the SIMS spectra were mainly the deprotonated molecule (M - H)- of arachidic acid, the protonated molecule (M + H)+ and the cationized ion (M - H + Ba)+. The Ba concentration in the bilayer was determined by X-ray photoelectron spectroscopy (XPS). When the Ba concentration increases, the intensity of (M - H)- and (M + H)+ strongly decreases but the intensity of (M - H + Ba)+ remains roughly constant. These results show that secondary ion mass spectrometry is very sensitive to the intermolecular interactions in LB films.