What are Ground and Excited States?

Mar 19, 2017 | Glossary of Spectroscopy Terms, Properties of Light

When talking about energy levels, the lowest level is called the ground state. At room temperature, everything (electrons, vibrations, etc.) is in the ground state. If the atoms or molecules can absorb energy, they can be promoted into a higher energy level, called an...

What is Raman Scattering?

Feb 26, 2017 | Glossary of Spectroscopy Terms, Properties of Light

Raman scattering is an inelastic scattering process that can be used to probe vibrational energy levels. All molecules can vibrate in various ways, but it takes energy to do so. Vibrations have energy levels, just like electrons do. To make molecules vibrate, a...

What is Reflection?

Feb 26, 2017 | Glossary of Spectroscopy Terms, Properties of Light

What is Diffuse Reflectance? Diffuse reflectance is a measurement technique used to analyze light scattered and reflected from the surface of a sample. Unlike specular reflection, which reflects light in a single direction, diffuse reflectance occurs when light...

What is Scattering?

Feb 26, 2017 | Glossary of Spectroscopy Terms, Properties of Light

In general, scattering is what happens when light is forced to deviate from a straight path, or forced to deviate from a reflection angle described by the law of reflection. For example, in the X-ray region, atoms can scatter the X-rays in a well defined pattern. This...

What is Transmittance?

Feb 26, 2017 | Glossary of Spectroscopy Terms, Properties of Light

Transmittance describes how much light passes through a sample unchanged. In other words, it is light that is not absorbed, scattered, or reflected. In most cases, the scattered and/or reflected light is miniscule and not significant. Transmittance is usually measured...

What is a Wave?

Feb 14, 2017 | Glossary of Spectroscopy Terms, Properties of Light

A wave is an oscillation in energy. In the context of electromagnetic radiation, the electric and magnetic fields oscillate. These oscillations repeat a pattern. For example, think of a sine wave. It starts at zero, goes up to a crest, goes down to a trough, and comes...