Raman spectroscopy of an ultrastable glass

We measured the vibrational spectra of ultrastable and conventional glasses of TPD (C (Formula presented.) H (Formula presented.) N (Formula presented.)). By using standard Raman spectroscopy in 90 (Formula presented.) scattering geometry, we measured the vibrational spectra of amorphous samples of TPD down to 6 cm (Formula presented.) at room temperature, in order to study the boson peak evolution as a function of glass stability and of temperature. At low wavenumbers, the spectrum of the ultrastable glass is less intense than that of the conventional one. We used the heterogeneous-elasticity theory to model the boson peak in the Raman spectra and in the specific heat data. Micro-Raman spectroscopy was exploited to study the high-wavenumber range. The obtained sharp peaks are identified with molecular vibrations and frustrated rotations within the molecules. In this wavenumber range, no appreciable differences were found between the two types of glasses.