Related Experiment Video
Updated: Jul 9, 2026
11:05
High-definition Fourier Transform Infrared (FT-IR) Spectroscopic Imaging of Human Tissue Sections towards Improving Pathology
Published on: January 21, 2015
Summary
Terahertz spectroscopy reveals strong absorption and dispersion in the organic ionic salt 4-N, N-dimethylamino-4?-N?-methyl-stilbazolium tosylate (DAST) above 1 THz. This suggests a single-phonon origin for its electro-optic properties.
Area of Science:
- Optoelectronics
- Materials Science
- Solid-State Physics
Background:
- Organic ionic salts are explored for advanced electro-optic applications.
- 4-N, N-dimethylamino-4?-N?-methyl-stilbazolium tosylate (DAST) is a promising organic material for electro-optic devices.
- Understanding the optical properties of DAST in the terahertz (THz) frequency range is crucial for its technological implementation.
Purpose of the Study:
- To measure the refractive index and absorption coefficient of DAST using terahertz time-domain spectroscopy.
- To investigate the temperature dependence of DAST's optical properties.
- To elucidate the origin of the strong far-infrared absorption and electro-optic properties of DAST.
Main Methods:
- Terahertz time-domain spectroscopy (THz-TDS) was employed.
- Measurements were conducted at room temperature and 83 K.
- Analysis focused on absorption coefficient and refractive index spectra.
Main Results:
- DAST exhibits strong absorption and dispersion for frequencies above 1 THz.
- Absorption strength remained consistent at both room temperature and 83 K.
- The observed resonances suggest a single-phonon origin.
Conclusions:
- The strong far-infrared absorption in DAST is attributed to a simple vibration of its anion and cation.
- These findings provide insights into the high-frequency electro-optic properties of DAST.
- DAST's characteristics make it a compelling material for THz optoelectronic applications.
Related Concept Videos
00:55IR Spectrum Peak Intensity: Amount of IR-Active Bonds
When infrared radiation is passed through a molecule, absorption occurs if the molecule's vibration leads to a substantial change in its bond dipole moment. Transitions between vibrational energy levels, typically corresponding to infrared frequencies (4000–400 cm−1), allow absorption if the vibration significantly alters the dipole moment, making the molecule infrared active. The molecular bonds have different stretching and bending vibrations, resulting in various peaks with varying...
01:09Infrared (IR) Spectroscopy: Overview
When electromagnetic radiation passes through a material, atoms or molecules transition from a lower to a higher energy state by absorbing radiation corresponding to the energy difference between the two states. The absorption of infrared (IR) radiation causes transitions between vibrational energy levels in a molecule. Therefore, IR spectroscopy is a useful analytical tool for determining the molecular structure of molecules.
Different compounds display unique properties due to their...
Different compounds display unique properties due to their...
01:25IR Spectrometers
There are two main infrared (IR) spectrophotometers: dispersive IR spectrometers and Fourier transform infrared (FTIR) spectrometers. In a dispersive IR spectrometer, a beam of infrared radiation produced by a hot wire is divided into two parallel equal-intensity beams using mirrors. One beam passes through the sample, while another is a reference beam. The beams then move through the monochromator, which separates the radiations into a continuous spectrum of different frequencies. The...
01:03IR Frequency Region: Fingerprint Region
IR spectra are divided into two main regions: the diagnostic region and the fingerprint region. The diagnostic region of the spectrum lies above 1500 cm−1. The absorptions resulting from single-bond vibrations of the N–H, C–H, and O–H stretch at higher wavenumbers and appear on the left side of the spectrum. The stretching absorptions of the C≡C and C≡N occur between 2100–2300 cm−1. In contrast, those arising from stretching absorptions of the C=O, C=N, and C=C occur between 1600–1850 cm−1.
The...
The...
01:13Attenuated Total Reflectance (ATR) Infrared Spectroscopy: Overview
Attenuated total reflectance (ATR) infrared spectroscopy is a powerful analytical technique used to study the composition of materials. It is widely employed in chemistry, materials science, forensic science, and other fields where sample characterization is required. ATR has several advantages over traditional transmission IR spectroscopy, including the requirement of little to no sample preparation and the ability to analyze a wide range of samples.
The ATR process begins by directing a beam...
The ATR process begins by directing a beam...
01:19IR Spectrum
When infrared (IR) radiation passes through a molecule, the bonds stretch or bend by absorbing the radiation. This absorption creates the molecule's absorption spectrum, which is the plot of its percentage transmittance versus wavenumber.
Transmittance is defined as the ratio of the radiant power passing through a sample to that from the radiation's source. Multiplying the transmittance by 100 gives the percent transmittance (%T), which varies between 100% (no absorption) and 0% (complete...
Transmittance is defined as the ratio of the radiant power passing through a sample to that from the radiation's source. Multiplying the transmittance by 100 gives the percent transmittance (%T), which varies between 100% (no absorption) and 0% (complete...