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Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy

Pippard relations applied to the lambda-phase transition in NH4Br.


PMID 18182320

Abstract

We establish here a linear variation of the specific heat C(P) with the frequency shifts (1/nu)(partial differential nu/partial differential T)P close to the lambda-phase transition in NH4Br (Tlambda = 234 K). This linear relationship is based on our spectroscopically modified Pippard relations. For this verification of our relations, we use our observed Raman frequencies of the lattice mode of nu7 (56 cm(-1)) and the internal mode of nu2 (1684 cm(-1)) in the NH4Br crystalline system. Our study given here indicates that the thermodynamic data can be obtained from the measured frequencies.