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The electron spin relaxation of Mn2+ in supercooled water adsorbed on silica gel and γ-alumina has been investigated. The correlation time for the modulation of the zero-field splitting tensor has been evaluated from the temperature and frequency dependence of the e.s.r. linewidth: τc= 1.4 ± 0.3 × 10–12 s at 25 °C has been extrapolated for bulk water solution. In the capillary adsorbed water, lineshape analysis suggests the existence of a distribution of crystal-field sites. The rate of interchange among differently relaxing sites is < 109 s–1. This suggests a long-range solid-water interaction which slows the mobility of water molecules up to 15–20 A from the surface.

The formation of the e.s.r. single absorption line at g= 2.003 previously observed on bismuth molybdates and MoO3 catalysts during interaction with olefins, has been investigated with CdMoO4. The signal is formed only by interaction of adsorbed olefins with adsorbed oxygen and arises from an ill-defined radical located on the catalyst surface. The easy oxidation of this radical under usual catalytic conditions suggests that it may be an intermediate in a pathway of non-selective oxidation of olefins. Comparison between catalytic and e.s.r. results suggests that adsorbed molecular oxygen is active in this oxidation.

The polarized single-crystal electronic and e.s.r. spectra of dichlorobis(triphenylphosphine oxide)copper(II) have been recorded and the spectral properties have been interpreted on the basis of a compressed tetrahedral geometry in C2 symmetry.