Buckling in a solid Langmuir monolayer: light scattering measurements and elastic model

Above a surface pressure threshold pi(c), we detect a buckled state in the low temperature solid phase of a phospholipid monolayer spread at the air-formamide interface. Stable ripples are observed with a Brewster angle microscope, and light scattering provides measurements pi(c) = 7 mNm(-1), wavelength Lambda approximate to 16 mu m and amplitude xi of a few nm for the deformation. A model, coupling the monolayer thickness and elongation, and consistent with the monolayer texture, is also presented.