Related Experiment Video
Updated: May 18, 2026
07:24
Hyperspectral Imaging as a Tool to Study Optical Anisotropy in Lanthanide-Based Molecular Single Crystals
Published on: April 14, 2020
Improved mode assignment for molecular crystals through anisotropic terahertz spectroscopy.
Rohit Singh1, Deepu Koshy George, Jason B Benedict
1Department of Physics, University at Buffalo, Buffalo, New York, USA.
The Journal of Physical Chemistry. A
|October 9, 2012
Summary
We studied the terahertz response of oxalic acid and sucrose crystals, finding good agreement between experimental and theoretical calculations. Oxalic acid
Area of Science:
- Solid-state physics
- Materials science
- Terahertz spectroscopy
Background:
- Terahertz (THz) spectroscopy is a powerful tool for probing low-frequency vibrational modes in materials.
- Understanding the anisotropic response of molecular crystals is crucial for their application in optical devices.
- Density functional theory (DFT) provides a theoretical framework for predicting material properties.
Purpose of the Study:
- To investigate the anisotropic terahertz response of oxalic acid and sucrose single crystals.
- To compare experimental results with theoretical calculations using solid-state DFT.
- To evaluate the potential of these materials for terahertz polarization manipulation.
Main Methods:
- Terahertz time-domain spectroscopy (THz-TDS) was performed on large, single crystals of oxalic acid and sucrose.
- Solid-state density functional theory (DFT) calculations were used to model the crystal phonon response.
- Measurements were conducted in the 0.2-3.0 THz frequency range.
Main Results:
- Good agreement was found between the experimentally observed anisotropic terahertz response and DFT calculations.
- Oxalic acid exhibits a large birefringence (Δn = 0.3), indicating potential for THz polarization control.
- Sucrose shows a smaller birefringence (Δn = 0.05), comparable to x-cut quartz. Oxalic dihydrate can be converted to anhydrous form.
- Anisotropic measurements aided in mode separation and symmetry determination for sucrose.
Conclusions:
- The study validates the use of DFT for predicting the terahertz phonon spectra of molecular crystals.
- Oxalic acid is a promising material for terahertz polarization manipulation due to its high birefringence.
- Anisotropic THz-TDS is effective for spectral analysis and symmetry assignment in complex molecular crystals.
Related Concept Videos
01:29Determination of Crystal Structures
In the late 1800s, the revelation that light extended beyond visible wavelengths led to the discovery of X-rays by Wilhelm Roentgen. Recognized as high-energy electromagnetic radiation with short wavelengths, X-rays prompted exploration into their interaction with crystals. Max von Laue proposed in 1912 that the periodic arrangement of atoms, ions, or molecules in crystals would cause them to diffract X-rays, a hypothesis confirmed through experiments with copper sulfate and zinc sulfide...
01:20¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
01:16IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
A covalently bonded heteronuclear diatomic molecule can be modeled as two vibrating masses connected by a spring. The vibrational frequency of the bond can be expressed using an equation derived from Hooke's law, which describes how the force applied to stretch or compress a spring is proportional to the displacement of the spring. In this case, the atoms behave like masses, and the bond acts like a spring.
According to Hooke's law, the vibrational frequency is directly proportional to the...
According to Hooke's law, the vibrational frequency is directly proportional to the...
02:18X-ray Crystallography
The size of the unit cell and the arrangement of atoms in a crystal may be determined from measurements of the diffraction of X-rays by the crystal, termed X-ray crystallography.
Diffraction
Diffraction is the change in the direction of travel experienced by an electromagnetic wave when it encounters a physical barrier whose dimensions are comparable to those of the wavelength of the light. X-rays are electromagnetic radiation with wavelengths about as long as the distance between neighboring...
Diffraction
Diffraction is the change in the direction of travel experienced by an electromagnetic wave when it encounters a physical barrier whose dimensions are comparable to those of the wavelength of the light. X-rays are electromagnetic radiation with wavelengths about as long as the distance between neighboring...
01:15¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.