Espectroscopia Raman de policristais de clorohidrato de L-cisteína sob altas pressões

Abstract

In this work we have studied the behavior of the vibrational modes (presentes) in the Raman spectra of policristals of L-cisteína.HCl, submited to severals pressure condictions between 0 and 6.86 GPa. For the pressure measure we have utilized a pressure cell with diamond extremes of the type National Burean Standard. We verify a significative change in practically all regions of the Raman spectra of the sample, around 0.8 GPa, inclusively in the region relationed to the lattice modes. This change in the spectra is a indicative of that a structural phase transition has ocurred in this pressure value. We also observe the arise of a band that was associated to a CC stretch vibrational and a band between 330 e 3400 cm−1 . Between 1.66 e 2.31 GPa, changes ocurried in some interne modes, however (não estejam) associated to some phase transition. We verify too, that some spectra presents smooth changes between 3.5 e 4.5 GPa. But, this changes don´t ocurred in the region of the lattice modes and so, we don´t associated it to symmetry crystal change. Finally, we make a study of descompression, we verify that the phase transition is reversible.