Broadband terahertz time-domain spectroscopy and low-frequency Raman scattering of glassy polymers: Boson peak of PMMA

ABSTRACT

The low-energy vibrational properties of polymethyl methacrylate (PMMA) were studied by terahertz time-domain spectroscopy and Raman scattering. The real and imaginary parts of a complex dielectric constant were accurately determined in the frequency range from 0.2 to 5.0 THz. The imaginary part of the dielectric constant shows a line-shape similar to the imaginary part of the Raman susceptibility measured by Raman scattering. These two spectra show broad peaks at about 2.3 THz. We also separately determined the Raman and far-infrared light-vibration coupling constants of the PMMA using the vibrational density of states determined by cold neutron inelastic scattering in the literature.

Keywords:

• THz dynamics experiments
• polymethyl methacrylate
• THz time-domain spectroscopy
• Raman scattering
• PMMA
• boson peak

Acknowledgments

This work was partially supported by a Grants-in-Aid for Young Scientists (B) (24740194) from JSPS and the Sasakawa Scientific Research Grant from The Japan Science Society.