Pre-resonance Raman studies of some mesogens-TB4A,TB7A and TB10A |
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| Authors: | S K Dash Ranjan K Singh P R Alapati A L Verma |
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| Institution: | Department of Physics , Memorial University of Newfoundland , St. John's NF, Canada, A1B 3X7 |
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| Abstract: | Pre-resonance Raman spectra of certain liquid crystalline compounds, TB4A, TB7A and TB10A, are reported. The anomaly observed in the pre-resonance Raman spectra in the three compounds was initially explained by the Albrecht-Hutley Model, but its failure leads us to explain the anomalous intensity enhancement mechanism by invoking an interference effect between a weak dipole-forbidden excited state and a nearby strong electronic level via vibrational modes. The presence of a 21Ag dipole-forbidden excited state in TB4A and TB10A is deduced after an elaborate discussion of their centro-symmetric structure. The structural difference of TB7A in comparison with TB4A and TB10A is also discussed by taking their X-ray data into consideration. |
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