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Title: Apparatus and method for quantitative measurement of small differences in optical absorptivity between two samples using differential interferometry and the thermooptic effect

Abstract

An apparatus and method for the measurement of small differences in optical absorptivity of weakly absorbing solutions using differential interferometry and the thermooptic effect has 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 pathlength 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.-5 cm.sup.-1 can then be determined in the presence of background absorptions in excess of 10.sup.-3 cm.sup.-1. In addition, the smallest absorption measured with the instant apparatus and method is about 5.times. 10.sup.-6 cm.sup.-1.

Inventors:
 [1];  [1]
  1. (Los Alamos, NM)
Issue Date:
Research Org.:
Los Alamos National Laboratory (LANL), Los Alamos, NM
OSTI Identifier:
864988
Patent Number(s):
4447153
Assignee:
United States of America as represented by United States (Washington, DC) LANL
DOE Contract Number:  
W-7405-ENG-36
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
apparatus; method; quantitative; measurement; differences; optical; absorptivity; samples; differential; interferometry; thermooptic; effect; weakly; absorbing; solutions; developed; sample; cells; placed; arm; interferometer; traversed; colinear; probe; heating; laser; beams; interrogation; recombined; forming; fringe; pattern; intensity; related; changes; pathlength; results; amounts; index; refraction; liquid; temperature; dependent; critical; feature; stabilization; path; drift; background; solvent; absorption; suppressed; factor; approximately; 400; solute; absorptivities; 10; -5; cm; -1; determined; presence; absorptions; excess; -3; addition; measured; instant; times; -6; temperature dependent; probe beam; laser beams; laser beam; optical path; fringe pattern; quantitative measure; quantitative measurement; /356/

Citation Formats

Cremers, David A., and Keller, Richard A. Apparatus and method for quantitative measurement of small differences in optical absorptivity between two samples using differential interferometry and the thermooptic effect. United States: N. p., 1984. Web.
Cremers, David A., & Keller, Richard A. Apparatus and method for quantitative measurement of small differences in optical absorptivity between two samples using differential interferometry and the thermooptic effect. United States.
Cremers, David A., and Keller, Richard A. Sun . "Apparatus and method for quantitative measurement of small differences in optical absorptivity between two samples using differential interferometry and the thermooptic effect". United States. https://www.osti.gov/servlets/purl/864988.
@article{osti_864988,
title = {Apparatus and method for quantitative measurement of small differences in optical absorptivity between two samples using differential interferometry and the thermooptic effect},
author = {Cremers, David A. and Keller, Richard A.},
abstractNote = {An apparatus and method for the measurement of small differences in optical absorptivity of weakly absorbing solutions using differential interferometry and the thermooptic effect has 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 pathlength 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.-5 cm.sup.-1 can then be determined in the presence of background absorptions in excess of 10.sup.-3 cm.sup.-1. In addition, the smallest absorption measured with the instant apparatus and method is about 5.times. 10.sup.-6 cm.sup.-1.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1984},
month = {1}
}

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