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A New Mechanism of Raman Enhancement and its Application
Author(s) -
Xu Yizhuang,
Wu Jinguang,
Sun Wenxiu,
Tao Dongliang,
Yang Limin,
Song Zengfu,
Weng Shifu,
Xu Zhenhua,
Soloway Roger D.,
Xu Duanfu,
Xu Guangxian
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20021202)8:23<5323::aid-chem5323>3.0.co;2-e
Subject(s) - raman spectroscopy , raman scattering , ion , population , materials science , chemistry , analytical chemistry (journal) , optics , physics , demography , organic chemistry , chromatography , sociology
Strong electronic Raman bands corresponding to the transition between 4 I 9/2 and 4 I 11/2 manifolds of Nd 3+ , caused by a Raman‐enhancement effect, are observed in the FT‐Raman spectrum of Nd 2 O 3 . Neither resonance enhancement (RR) nor surface enhancement (SERS) accounts for the Raman enhancement observed here. We propose a new mechanism of Raman enhancement called the “feed‐back” mechanism. A YAG laser excites the final state of the Raman transition ( 4 I 11/2 of Nd 3+ ) to the 4 F 3/2 state and causes a significant decrease in the population of Nd 3+ at the 4 I 11/2 state. This causes the population ratio of Nd 3+ at 4 I 9/2 and 4 I 11/2 to deviate from the value required by Boltzmann's law. To restore equilibrium, Raman scattering is enhanced so that more Nd 3+ ions are brought from the 4 I 9/2 state to the 4 I 11/2 state. This hypothesis gets support from the temperature‐variable FT‐Raman spectroscopic results. Additionally, obvious differences between the Stokes and anti‐Stokes Raman spectrum of Nd 3+ provide further evidence to support the feed‐back mechanism. The Raman‐enhancement effect confers on the electronic Raman bands a special ability to reflect the variation of coordinated structure around metal ions. The structural variations in polymer–metal ion composites and biomineralization systems have been investigated by using the electronic Raman bands.