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A second harmonic analyzer for the detection of non‐centrosymmetry
Author(s) -
Dougherty J. P.,
Kurtz S. K.
Publication year - 1976
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889876010789
Subject(s) - spectrum analyzer , second harmonic generation , harmonic , materials science , phase (matter) , phase transition , analytical chemistry (journal) , optics , condensed matter physics , chemistry , physics , acoustics , chromatography , laser , organic chemistry
The existence of optical second harmonic generation has been shown to be a highly reliable and sensitive physical test for the detection of crystalline non‐centrosymmetry. A second harmonic analyzer has been constructed which can resolve space group ambiguities arising from Friedel's Law with a confidence level greater than 99%. The system has been optimized for use with powdered crystalline samples so as to obviate the need for large single crystals and thus facilitates rapid determination of crystalline non‐centrosymmetry. The present analyzer can routinely detect second harmonic generation at levels 1/1000 of that generated in a quartz standard, this is about an order of magnitude increase over previously reported systems. Data are reported on several materials including dibenzyldisulfide, and [(C 6 H 5 ) 3 P] 3 CuBF 4 . The detection of structural phase transitions with the second harmonic analyzer is reported for BaTiO 3 , colemanite and phenanthrene. Second harmonic generation in the `cubic' phase of BaTiO 3 promises to be a powerful tool for determining the dynamics of the ferroelectric phase transition. It is the most direct method for establishing the existence or nonexistence of microscopic polar regions well above the Curie point in a nominally centrosymmetric phase.