Apparatus and method for quantitative measurement of small differences in optical absorptivity between two samples using differential interferometry and the thermooptic effect
An apparatus and method for the measurement of small differences in optical absorptivity of weakly absorbing solutions using differential interferometry and the thermooptic effect have been developed. Two sample cells are placed in each arm of an interferometer and are traversed by colinear probe and heating laser beams. The interrogation probe beams are recombined forming a fringe pattern, the intensity of which can be related to changes in optical path length of these laser beams through the cells. This in turn can be related to small differences in optical absorptivity which results in different amounts of sample heating when the heating laser beams are turned on, by the fact that the index of refraction of a liquid is temperature dependent. A critical feature of this invention is the stabilization of the optical path of the probe beams against drift. Background (solvent) absorption can then be suppressed by a factor of approximately 400. Solute absorptivities of about 10[sup [minus]5] cm[sup [minus]1] can then be determined in the presence of background absorptions in excess of 10[sup [minus]3] cm[sup [minus]1]. In addition, the smallest absorption measured with the instant apparatus and method is about 5 [times] 10[sup [minus]6] cm[sup [minus]1]. 6 figs.
- DOE Contract Number:
- W-7405-ENG-36
- Assignee:
- Dept. of Energy, Washington, DC (United States)
- Patent Number(s):
- US 4447153; A
- Application Number:
- PPN: US 6-386371
- OSTI ID:
- 7246965
- Resource Relation:
- Patent File Date: 8 Jun 1982
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
INTERFEROMETERS
DESIGN
OPERATION
SOLUTIONS
OPTICAL PROPERTIES
ABSORPTION
ACCURACY
CALIBRATION
LASER RADIATION
REFRACTIVE INDEX
STABILIZATION
DISPERSIONS
ELECTROMAGNETIC RADIATION
MEASURING INSTRUMENTS
MIXTURES
PHYSICAL PROPERTIES
RADIATIONS
SORPTION
400102* - Chemical & Spectral Procedures