New terahertz dielectric spectroscopy for the study aqueous solutions

TL;DR

This paper introduces a high-precision, tunable terahertz dielectric spectrometer capable of studying aqueous solutions and biomolecular dynamics with exceptional resolution and sensitivity across a broad frequency range.

Contribution

The development of a novel terahertz dielectric spectrometer with high spectral resolution, high signal-to-noise ratio, and precise temperature control for studying aqueous solutions.

Findings

Measured water absorption and refractive index from 5 GHz to 1.12 THz.

Achieved spectral resolution below 100 Hz.

Provided accurate measurements of strongly absorbing aqueous solutions.

Abstract

We present a development of a high precision, tunable far-infrared (terahertz) frequency-domain dielectric spectrometer for studying the dynamics of biomolecules in aqueous solutions in the gigahertz-to-terahertz frequency. As a first application we report on the measurement of the absorption and refractive index for liquid water in the frequency range from 5 GHz to 1.12 THz (0.17 to 37.36 cm-1 or 0.268 to 60 mm). The system provides a coherent radiation source with a power up to 20 mW in the gigahertz-to-terahertz region. The power signal-to-noise ratio of our instrument reaches 1015 and the system achieves a spectral resolution of less than 100 Hz. The temperature of samples can be controlled precisely with an error bars of 0.02 oC from above 0 oC to 90 oC. Given these attributes, our spectrometer provides unique capabilities for the accurate measurement of even very strongly absorbing materials such as aqueous solutions.