A Fourier Transform Infrared Spectrometer with a Composite Interferometer for Soft Mode Studies

Abstract

The Fourier transform infrared spectrometer has a new design of composite construction which allows it to be alternatively utilized for both the amplitude-divided two-beam interferometer and the polarization-divided two-beam one. A wide range of spectral wavenumbers to 4 cm -1 can be covered with changes of beam splitters, light sources and detectors except for a change of the main optical configuration. By means of the spectrometer with a silicon bolometer, the soft phonon mode which associates the structural phase transition has been measured in ferroelectric Li 2 Ge 7 O 15 single crystals. The performance of the spectrometer for soft mode studies is estimated.