What is the difference between Raman spectroscopy and infrared spectroscopy?

Raman spectroscopy depends on a change in polarizability of a molecule, whereas IR spectroscopy depends on a change in the dipole moment. Raman spectroscopy measures relative frequencies at which a sample scatters radiation, unlike IR spectroscopy which measures absolute frequencies at which a sample absorbs radiation.

How are Raman and IR complementary?

Raman spectroscopy is often considered to be complementary to IR spectroscopy. Infrared radiation causes molecules to undergo changes in their vibrational and rotational motion. When the radiation is absorbed, a molecule jumps to a higher vibrational or rotational energy level.

What are the advantage of Raman spectroscopy over IR spectroscopy?

A big advantage of using Raman over IR is that the sample preparation is much easier and less time-consuming. Speed is crucial in the analysis because runtimes need to be as short as possible so that more samples can be analyzed.

What does Raman spectroscopy measure?

Raman spectroscopy is an analytical technique where scattered light is used to measure the vibrational energy modes of a sample. Raman spectroscopy can provide both chemical and structural information, as well as the identification of substances through their characteristic Raman ‘fingerprint’.

Which is better Raman or IR spectroscopy?

The differences between Raman and IR spectroscopy: The fundamental principles that govern each method – the Raman effect is weak, resulting from an inelastic raman scattering process that occurs when light interacts with molecules; IR spectroscopy is a stronger technique that relies on absorption of light by molecules.

Why is IR spectroscopy also called vibrational spectroscopy?

A molecule can vibrate in many ways, and each way is called a vibrational mode. Unsymmetrical diatomic molecules, e.g. CO, absorb in the IR spectrum. More complex molecules have many bonds, and their vibrational spectra are correspondingly more complex, i.e. big molecules have many peaks in their IR spectra.

Is Raman spectroscopy quantitative?

Raman spectroscopy is both qualitative and quantitative. The general spectrum profile (peak position and relative peak intensity) provides a unique chemical fingerprint which can be used to identify a material, and distinguish it from others.