Time-resolved terahertz spectroscopy: Polymorphic solid state phase transitions in carbamazepine

The polymorphic modifications of carbamazepine show distinct spectral features in the far infrared between 2 and 130 cm^-1. Using time-resolved terahertz pulsed spectroscopy the enantiotropic solid state phase transition between two polymorphic forms was recorded. The terahertz spectra revealed that the solid state conversion follows a two step mechanism: form III sublimates and then condenses in a second step as form I. The sublimation and condensation steps follow different kinetics.