Zengyan Zhang

Shift in low-frequency vibrational spectra of transition-metal zirconium compounds

The far-infrared terahertz(THz) spectra of ZrC, ZrN, ZrO2, and ZrF4 have been measured using terahertz time-domain spectroscopy. The characterization of the frequency-dependent power absorption, index of refraction and complex dielectric function in the frequency range 0.1–2.0THz are obtained. A standard Drude-Lorentz model gives a good fit on the transmission measurement results. We first observe the shift in the low-frequency vibrational spectra of different zirconium compounds. We analyze that the influence of the anion on the vibration modes causes the shift in low-frequency vibrational spectra of zirconic compounds.

The coordination and phase separation in nylon-copper chloride system

In this paper, the spectroscopic and morphological behaviors of nylon 6-copper chloride systems have been investigated. The temperature-variable Fourier transform infrared (FT-IR) spectra of nylon-copper chloride systems shows that a new band of 1600 cm(-1) appeared between the amide I band at about 1639 cm(-1) and the amide II band around 1552 cm(-1) compared with the FT-IR spectra of pure nylon, which indicates that there was the coordination between copper ions and the amide groups of nylon. The processed spectra of extended X-ray absorption fine-structure of copper ions at K edge showed that one copper ion can coordinate two oxygen atoms and two chloride ions in nylon 6-copper chloride systems, Phase separation in nylon-copper chloride systems was observed by using near-field scanning optical microscopy

Terahertz Time-Domain Spectroscopy of Four Hydroxycinnamic Acid Derivatives

The well-resolved absorption spectra of the hydroxycinnamic acid (HCA) derivatives, caffeic acid, ferulic acid, sinapic acid and chlorogenic acid, were measured over the frequency region from 0.3 to 2.0xa0THz at 294xa0K with terahertz time-domain spectroscopy (THz-TDS). Theoretical calculation was applied to assist the analysis and assignment of the individual THz absorption spectra of the HCA derivatives with density functional theory (DFT). The distinctive spectral features were originated from the collective motion of molecules held together by hydrogen bonds. The real and imaginary parts of dielectric function of the four HCA derivatives were also obtained.

Far-infrared characteristics of NaCl and alkali halide

The optical and dielectric properties of NaCl and alkali halide are studied by Terahertz time-domain spectroscopy (THz-TDS) technique from 0.3 THz to 1.4 THz. The absorption spectral features of measured samples are discussed based on their characteristic and common features. Further, the measured complex refractive index and dielectric functions of NaCl are well fitted by a standard Lorentz model. Theoretical calculations indicate that characteristic phonon resonance of NaCl is dominated by the transverse optical phonon mode at 5.10 THz.