Relaxation Resonance Properties of the Dielectric Response of Water
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xation Resonance Properties of the Dielectric Response of Water A. A. Volkova, A. A. Vasina, *, and A. A. Volkov, Jr.b aProkhorov
General Physics Institute, Russian Academy of Sciences, Moscow, 119991 Russia bMoscow State University, Moscow, 119991 Russia *e-mail: [email protected] Received April 10, 2020; revised April 29, 2020; accepted May 27, 2020
Abstract—Broadband terahertz infrared absorption spectra of liquid water are described using the nonstandard Frenkel gas–solid model for water, supplemented by the interconversion of molecules and ions due presumably to the mixed translational–vibrational motion of molecules in liquids. The periods of water molecule retention by hydration and ionic shells are calculated. DOI: 10.3103/S1062873820090373
INTRODUCTION The dielectric response (i.e., a medium’s reaction to sounding electromagnetic radiation in the form of the frequency spectra of the coefficients of absorption and refraction) is one of the main properties of liquid water. Due to the electromagnetic nature of the substance, this response provides direct information about the processes occurring in it. There are volumes of such information for water; despite decades of research, however, it has yet to be fully understood at the molecular level [1]. As the problem in this work, we consider the absorption spectrum of water. This spectrum is presented in Fig. 1, in the frequency band of 10 9–1014 Hz (from microwaves to the optical range) in the form of a spectrum of the imaginary ε″(ω) part of dielectric permittivity. Water’s dielectric loss has been studied in this form for decades [2–12], and she results have been compiled in databases [13, 14]. The image in Fig. 1 is formed by four absorption bands. The low frequencies are dominated by socalled Debye relaxation band R1 (Relaxation-1) with a maximum at frequency νD ~ 20 GHz at room temperature. This absorption is associated with the heating of water by microwave radiation (MW heating [15]). The effect is widely known and used for heating water-containing media in household and industrial microwave ovens [16]. The Debye relaxation makes a major contribution to the static dielectric permittivity (~90%). The high dielectric permittivity (ε' ~ 80 at room temperature) is considered to be responsible for the high solubility of water. It is assumed that high ε' effectively reduces the energy of ion–ion interaction.
On the high frequency side (around ν2 ~ 0.6 THz), weak absorption band R2 (Relaxation-2) borders the Debye relaxation zone. In Fig. 1, it merges with R1 and is barely visible. Band R2 is well known to researchers as an integral detail of Relaxation-1 [9, 10].
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(a) ε'' 10 R1 R2
1 273–373 К
L1
L2
(b)
σ, Ω–1 m–1
L2
1000
L1 500 R1 0
108
109
1010
1011
R2
1012
1013 1014 Frequency, Hz
Fig. 1. Frequency spectra of dielectric losses of liquid water (through 10 K, from database [13, 14]): (a) in the traditional representation ε″(ω) and (b) in the form of dynamic conductivity σ(ω).
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VOLKOV et al.
Relaxation bands R1 and R2 contin
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