Built-Up Films of Barium Stearate and Their Optical Properties

作者：Katharine B. Blodgett, Irving Langmuir · 发表于：Physical Review · 年份：1937 · DOI：10.1103/physrev.51.964 · 被引用次数：1060 · 研究领域：Surfactants and Colloidal Systems

The technique of depositing successive single layers of molecules of various stearates on a solid surface is described. Films containing 3001 layers have been built of barium-copper stearate. A photograph shows films built in a series of steps having intervals of 2 molecular layers. The contrast of the steps is plainly visible when the slide is illuminated by polarized light at angles near grazing incidence. By measuring the angles at which films containing known numbers of layers reflect minimum intensity of monochromatic light for the first five interference fringes, the thickness per layer and refractive index can be calculated with great accuracy. The thickness per layer of barium stearate was found to be 24.40A. The presence of traces of foreign substances in the water affect the spacing by 1 to 3 percent. The films are uniaxial crystals, the optic axis being perpendicular to the surface on which the films are built. The refractive index of the ordinary ray, ${n}_{1}$, and of the extraordinary ray in a direction perpendicular to the axis, ${n}_{3}$, are ${n}_{1}=1.491$, ${n}_{3}=1.551$. Equations are given which describe the refraction of the extraordinary ray, the intensity of the rays reflected from the upper surface and from the film solid boundary, the phase change at the boundaries, Brewster's angle, and other special properties of birefringent films. The intensity of the light and dark fringes reflected by films built on a series of glasses of known refractive indi...