Nonlinear optical studies of monomolecular films under pressure
- Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States)
Nonlinear optical techniques (second-harmonic and sum-frequency generation) have been used to study the structure of organic molecules that are confined and compressed between a lens and a flat surface. The molecules studied include self-assembled monolayers of [ital n]-octadecyltriethoxysilane and Langmuir-Blodgett films of stearic acid, octadecylalcohol, octadecylamine, and a liquid-crystal molecule 4[prime]-[ital n]-octyl-4-cyanobiphenyl (8CB). The contact area created by elastic deformation of the flat surface and lens under pressure was large enough to contain the entire laser beam ([gt]100 [mu]m radius at [approx]10 MPa for [ital R]=15 cm). Under these conditions, the sum-frequency generation (from CH[sub 3] and OH stretch modes) and second-harmonic generation (8CB) signals were found to decrease by a factor between 100 and 1000 times the original signal. This indicates vanishing of the second-order monolayer susceptibility due to disorder of the head groups and/or flattening of the molecular axis so that they lie parallel to the surface. The phenomenon was reversible and the nonlinear signals recovered completely upon removal of the pressure.
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6493584
- Journal Information:
- Physical Review, B: Condensed Matter; (United States), Vol. 51:12; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC COMPOUNDS
MOLECULAR STRUCTURE
ELASTICITY
HARMONIC GENERATION
LASER RADIATION
LIQUID CRYSTALS
NONLINEAR OPTICS
PRESSURE DEPENDENCE
VIBRATIONAL STATES
CRYSTALS
ELECTROMAGNETIC RADIATION
ENERGY LEVELS
EXCITED STATES
FLUIDS
FREQUENCY MIXING
LIQUIDS
MECHANICAL PROPERTIES
OPTICS
RADIATIONS
TENSILE PROPERTIES
360606* - Other Materials- Physical Properties- (1992-)