High temperature phase transition in monohydrated L-asparagine crystal

Raman scattering has been used to investigate monohydrated L-asparagine single crystals for temperatures above 300 K in the spectral region between 20 and 3500 cm−1. It is found that several phonon peaks characterizing the orthorhombic D24 room temperature phase are notably suppressed in intensity for temperatures higher than ∼363 K. This is evidence of a new phase in this hydrogen-bonded crystalline system, and the transition is compared with both the high-pressure and the low-temperature phase transitions undergone by the crystal.