Temperature Dependence of the Linewidth of the Eg Modes of the Raman Spectra for NaNO┣D213D2 Crystal
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The first-order Raman spectra of <I>E<SUB>g</SUB></I> (2) (186cm<SUP>-1</SUP>) and <I>E<SUB>g</SUB></I> (4) (1385cm<SUP>-1</SUP>) modes in NaNO<SUB>3</SUB> crystal were measured in the temperature range of 77-473 K and the linewidths at these temperatures were obtained. The temperature dependence of the linewidths was analyzed using the phonon dispersion curves calculated on the basis of a modified rigid-ion model. The results showed that the temperature dependence of the linewidth is caused by the cubic anharmonic term in the crystal potential energy for external <I>E<SUB>g</SUB></I> (2) mode (186cm<SUP>-1</SUP>), while it is caused by the cubic anharmonic term and quartic one in the crystal potential energy for internal <I>E<SUB>g</SUB></I> (4) mode (1385cm<SUP>-1</SUP>). This suggested that since a NaNO3 crystal has a very large energy gap between internal modes and external ones with three phonon process, decay channel for internal modes has a stronger tendency to affect on phonon lifetime than that in the case of external modes.
- Bunko Kenkyu
Bunko Kenkyu 48(6), 246-254, 1999-12-15
The Spectroscopical Society of Japan