Molecular polarizability investigation of polar solvents: water, ethanol, and acetone at terahertz frequencies using terahertz time-domain spectroscopy
Tianyao Zhang, Zhaohui Zhang, Xiaoyan Zhao, Can Cao, Yu Yang, Xingyue Li, Ying Li, Yan Chen, Qing Li Ren
Abstract
In this paper, we present the application of transmissive terahertz (THz) time-domain spectroscopy for determining molecular polarizability for three widely applied solvents: water, ethanol, and acetone. Molecular polarizabilities of those solvents are obtained from the refractive index by using the Lorentz–Lorenz equation. The measured THz molecular polarizabilities are comparable with theoretical values estimated with both the first principle calculation and the atomic polarizability additive model. The THz spectra are presented over frequencies ranging from 0.3 to 1.2 THz ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mn>10</mml:mn> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>−</mml:mo> </mml:mrow> <mml:mn>40</mml:mn> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">c</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> ). The molecular polarizability at 1.0 THz is determined as <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>3.81</mml:mn> </mml:mrow> <mml:mo>±</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>0.03</mml:mn> </mml:mrow> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>7.04</mml:mn> </mml:mrow> <mml:mo>±</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>0.07</mml:mn> </mml:mrow> </mml:math> , and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>7.9</mml:mn> </mml:mrow> <mml:mo>±</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>0.2</mml:mn> </mml:mrow> <mml:mspace width="thickmathspace"/> </mml:math> Å 3 for water, ethanol, and acetone, respectively.