Temperature dependence of the damping constant and the order parameter close to the lambda phase transitions in ammonium halides

Date

2006-10-01

Author

Yurtseven, Hasan Hamit

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This study gives our calculation for the damping constant, using the expressions derived for an Ising pseudospin-phonon coupled system in the ammonium halides (NH4Cl and NH4Br). For this calculation of the damping constant, we use the temperature dependence of the order parameter calculated from the molecular field theory. We predict here the damping constants for the v(5) (174 cm(-1)) and v(5) (177 cm(-1)) Raman modes of NH4Cl and NH4Br, respectively, below T-lambda and compare them with our observed bandwidths measured as a function of temperature for those phonon modes at zero pressure.

Subject Keywords

Instrumentation, Analytical Chemistry, Spectroscopy, Atomic and Molecular Physics, and Optics

URI

https://hdl.handle.net/11511/36136

Journal

SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY

DOI

https://doi.org/10.1016/j.saa.2005.10.054

Collections

Department of Physics, Article

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Analysis of the Raman intensities near the phase transitions in ammonium halides Yurtseven, Hasan Hamit (Elsevier BV, 2008-12-01) This study concentrates on the temperature dependence of the Raman intensities for the lattice modes in ammonium halides (NH4Cl and NH4Br) close to phase transitions, We predict their intensities using the results of a shell model for the Raman polarizability within the framework of an Ising pseudospin-phonon coupled model.
Raman frequency shifts of an internal mode near the tricritical and second order phase transitions in NH4Cl Yurtseven, Hasan Hamit (Elsevier BV, 2005-12-01) This study gives our analysis for the frequency shifts of the nu(2)(1708 cm(-1)) Raman mode in NH4Cl close to its tricritical (P = 1.6 kbar) and second order (P = 2.8 kbar) phase transitions. From our analysis, we extract the values of the critical exponent which describes the critical behavior of the Raman frequency shifts for this internal mode for the pressure conditions studied in NH4Cl. Our exponent value of alpha approximate to 0.2 for the tricritical phase transition is close to the values of 1/16 (T...
Spectroscopic modification of the Pippard relation applied for the translational mode in ammonia solid II near the melting point Yurtseven, Hasan Hamit; Yıldız, İlker (Elsevier BV, 2005-09-01) This study gives our calculation for the frequency shifts 1/V(partial derivative v/partial derivative T)(P) and the specific heat C-p near the melting point in the ammonia solid II. We establish a linear relationship between C-p and 1/v(partial derivative v/partial derivative T)(P) using the Raman frequencies of the translational mode which we calculated in this system. This leads to the validity of the spectroscopic modification of the first Pippard relation in the ammonia solid II near the melting point. ...
Bandwidths studied as a function of temperature in ammonium halides near T-lambda Yurtseven, Hasan Hamit (Elsevier BV, 2005-12-01) This study gives our analysis of the Raman bandwidths using the soft mode-hard mode coupling model applied to ammonium halides. The temperature dependence of our observed bandwidths for the nu(5)(174 cm(-1)) Raman mode of NH4Cl and nu(5)(177 cm(-1)) Raman mode of NH4Br, is analyzed close to phase transitions. From our analysis, we obtain beta = 0.13 as the values of the critical exponent for the order parameter in the first order phase region for the ammonium halides.

Citation Formats

H. H. Yurtseven, “Temperature dependence of the damping constant and the order parameter close to the lambda phase transitions in ammonium halides,” SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, pp. 421–427, 2006, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/36136.