New p-Ge THz laser spectrometer for the study of solutions:: THz absorption spectroscopy of water -: art. no. 063110

We present the development of a high power, tunable far-infrared p-germanium laser spectrometer for the study of dissolved biomolecules in the THz range. As a first application we report on the measurement of the absorption coefficient alpha for liquid water in the frequency range from 81 to 96 cm(-1). Using the p-Ge laser spectrometer we were able to penetrate through layers of up to 100 mu m thickness. We discuss the advantages and the limitations of this THz spectrometer. We present an analysis of the experimental data based on a chi(2) test to provide an objective procedure to minimize the influence of systematic effects, for example of interference due to multiple reflections within the sample chamber. The measured absorption coefficient alpha lies between (410 +/- 6) and (490 +/- 6) cm(-1) at 81 and 96 cm(-1), respectively. (c) 2005 American Institute of Physics.