ODMR and resonance Raman spectroscopy of chlorophyll b on graphite

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Abstract
Zero‐field optically detected magnetic resonance (ODMR) and resonance Raman spectroscopy are used to study the adsorbate/substrate system chlorophyll b on highly oriented pyrolytic graphite. Chlorophyll b was applied to the conductive basal surface of the graphite using Langmuir–Blodgett techniques in which both the chlorophyll–chlorophyll and chlorophyll–graphite spacing could be varied. ODMR data reveal changes in chlorophyll b triplet state dynamic features which in the isolated molecule are determined by spin‐orbit coupling mechanisms. The possibility of energy transfer among adsorbed species is also suggested. These results are shown to depend not only upon the distance of the molecule from the surface, but also upon the intermolecular distance of photoexcited adsorbates. The resonance Raman spectrum leads to a plausible orientation of the adsorbed chlorophyll unit with respect to the graphite surface.