Orientational arrangement of long-chain fluorescein molecules within the monolayer at the air/water interface studied by the SHG technique

Orientational arrangement of long-chain Fluorescein O322 molecules within t he monolayer at the air/water interface induced by the compression process was studied by surface second harmonic generation. Compression does not cha nge the average tilt angle of the chromophore in any significant way, but i t induces the alignment of the chromophore along a preferred direction perp endicular to the compression direction, originating the in-plane optical an isotropy. A model has been proposed on the orientational ordering of Fluore scein O322 molecules within the monolayer induced by the compression proces s.