Raman observation of a new (ζ) polymorph of glycine?

A Raman spectroscopy study has proven, that on increasing hydrostatic pressure up to ∼3 GPa γ-glycine undergoes a phase transition into δ-polymorph, which on decompression down to 0.62 GPa transforms into another form, supposed to be a previously unknown polymorph termed ζ-glycine. The formation of this new form was observed also visually using optical microscopy and is in an agreement with the data from X-ray powder diffraction. On further decompression, δ- and ζ-forms coexisted in the pressure range between 0 and 0.62 GPa. The ζ-form of glycine was preserved at ambient conditions for at least 3 days.