Theory of Molecular Spectroscopy

Basic Theory of Molecular Spectroscopy

From the mid- 1950s, JASCO has been developing instruments and applications for some of the most important areas of molecular spectroscopy, including infra-red (FTIR), Raman, fluorescence, UV-visible/near infra-red, and chiral spectroscopy.

The evaluation of chirality is an important area in molecular spectroscopy because it is used in the development of biomolecules that are useful as new medicines, and for materials that can be used in novel technologies for applications in material science. Chiral spectroscopy includes diverse techniques such as optical rotation dispersion (ORD) and polarimetry, circular dichroism (CD) – both electronic and vibrational (VCD), as well as circularly polarized luminescence (CPL).

FTIR IconFTIR Spectroscopy

FTIR is concerned with the vibration of molecules.  Each functional group has its own discrete vibrational energy which can be used to identify a molecule through the combination of all of the functional groups. This makes FTIR microscopy ideal for sample ID, multilayer film characterization, and particle analysis.

Raman IconConfocal Raman Microscopy

This technique offers a number of significant advantages over other spectroscopic or optical microscopy techniques, as it can be used for chemical or molecular analysis encompassing depth profiling and microscopic area mapping of samples with a spatial resolution of as little as 1 μm.

IR Microscope IconIR Microscopy

FTIR is concerned with the vibration of molecules.  Each functional group has its own discrete vibrational energy which can be used to identify a molecule through the combination of all of the functional groups. This makes FTIR microscopy ideal for sample ID, multilayer film characterization, and particle analysis.

Circular Dichroism Icon

Circular Dichroism Spectroscopy

Circular dichroism spectroscopy (CD) is an essential analytical technique used to analyze chirality in molecules through their optical activity.

VCD Icon

Vibrational Circular Dichroism Spectroscopy

Vibrational circular dichroism (VCD) is a spectroscopy technique used to measure the absorption difference between left-handed and right-handed circularly polarized light in the infrared region. This is distinguished from electronic circular dichroism (ECD or CD), which focuses on the ultraviolet region.

FP Spectroscopy

Fluorescence Spectroscopy

Fluorescence spectroscopy is routinely used for studying structural changes in conjugated systems, aromatic molecules, and rigid, planar compounds due to alterations in temperature, pH, ionic strength, solvent, and ligands.

UV Vis Icon

UV/Visible Spectroscopy

UV-Visible/NIR spectroscopy can be divided into ultraviolet, visible, and near-infrared regions of the spectrum, depending on the wavelengths used. since its frequency is close to the overtone frequency of many natural vibrations, weak substance-specific absorption bands can be detected. It can therefore be used for non-destructive measurements, such as determining the sugar, lipid, protein content of foodstuffs and for identifying medicinals.

ATR Colored Icon Small

ATR FTIR Method

There are various FTIR methods that can be used to identify foreign material or contaminants. FTIR microscopy is used for foreign material where the size is in the order of few microns, but when a sample with foreign material can be observed by the naked eye, the particle type is typically greater than several hundred microns and does not require an FTIR microscope.  An ATR FTIR method may be a suitable alternative and offers advantages such as minimal sample preparation, non-destructive measurement, and easy handling.

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Circularly Polarized Luminescence

In recent years, circularly polarized luminescence (CPL) spectroscopy has also attracted a great deal of attention. Whereas CD spectroscopy provides information about the structure of optically active substances in the ground electronic state, CPL spectroscopy provides information about excited states. The two methods are therefore complementary to each other.