Molecular packing in lead arachidate lsqb;(C19H39COO)2Pbrsqb; Langmuir Blodgett monolayer films transferred to glass substrates has been investigated using xhyphen;ray photoemission spectroscopy. It was observed that the degree of salt formation was a sensitive function of the subphasepH reaching a maximum at apH of nearly 5.8. The loss features in the C 1score level spectra of the films were clearly defined for films consisting of purely metal salt of arachidic acid while they became progressively diffused as the subphasepH was reduced. The blurring of the C 1sloss features has been explained as arising due to disorder introduced into the alkyl chains of lead arachidate molecules by the evaporation of acid molecules under ultrahigh vacuum. This leads to changes in the quasi onehyphen;dimensional electronic band structure in such molecular crystal films. A comparison is made with results obtained on cadmium arachidate and arachidic acid monolayer Langmuir Blodgett films. It is thus shown that molecular packing in Langmuir Blodgett films may be investigated using core level loss spectroscopy.
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