SURFACE CRYSTALLIZATION OF LIQUID N-ALKANES AND ALCOHOL MONOLAYERS STUDIED BY SURFACE VIBRATIONAL SPECTROSCOPY

Infrared-visible sum-frequency generation (SFG) has been used to obtai n the surface vibrational spectra of CH stretches for liquid n-eicosan e and a monolayer film of 1-dodecanol in equilibrium with an excess dr op on water. The SFG data for surface freezing of eicosane represent a unique study of ordering among nonpolar surface molecules and are con sistent with the formation of a solid monolayer of nearly vertical, al l-trans molecules at the free liquid surface. For the dodecanol film, the result indicates that the alcohol molecules are nearly all-trans a nd erect both before and after surface crystallization.