There are numerous interactions between EM and matter.  These include some of the most commonly used interactions in instrumentation including  absorption, transmission/refraction, reflection, and emission.  Absorption occurs when matter transforms EM energy into internal energy (such as thermal energy) through an absorber.  Transmission and refraction are a function of the amount, wavelength, and angle of which energy (or light) pass through matter.  Reflection is the amount measurement of the amount of energy reflected matter and emission is the change in energy state as the incident energy passes through  matter.  All of these processes become the basis for some form of detection or spectroscopy measurement technique.

Other types of spectroscopy interactions include elastic scattering (similar to reflection) where the incident beam is scattered within the target material rather than just reflected.  Inelastic scattering also involves the measurement of scattering but is as part in a change in wavelength.  Impedance is the slowing of the transmitting of energy. Resonance spectroscopy is characterized by radiant energy being a radiating field between quantum states of the material.  Finally, there is nuclear spectroscopy that utilizes the nuclei to determine the properties of matter. 

Spectroscopy techniques are divided into atomic and molecular spectroscopy depending on the target to be measured and the material being tested.  Molecular spectroscopy studies the interaction of energy and matter between molecules and is most often found in techniques measuring organic molecules and includes instruments such as Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), UV and visible light spectroscopy. 

Atomic spectroscopy studies the energy and matter interactions between atoms.  Most of the atomic spectroscopy techniques are applied to the study of elemental composition.  The instruments under atomic spectroscopy include atomic absorption (AA), X-ray fluorescence (XRF), and inductively coupled spectroscopy (ICP). 

Spectrometry instruments are often further divided defined by the type of interactions they produce and the type of energy which is measured like X-ray Fluorescence (XRF) which measures x-rays and the amount of fluorescent energy a material emits during exposure.  Some techniques focus on a narrow band of interactions (such as emission only) or a small part the EM spectrum (like X-rays) while other techniques monitor an array of interactions and wavelengths on the spectrum. 

The most common atomic spectroscopy techniques measure total concentration of elements which are important for health and safety such as heavy metals (As, Cd, Cr, Hg, & Pb) or nutrient elements (K, Fe, Cu, etc.) Depending on the sample and the target concentration these elements are measured by different instruments where AA and ICP target higher concentrations and tandem techniques such as ICP-MS target lower concentrations.

Join Spex in celebrating Spectroscopy week with a deeper look into atomic spectroscopy with our app note on Heavy Metals in Hot Sauce & Chili Powder, our podcast on Hot Sauce Chemistry, and our flyers about sample preparation for elemental analysis with our GenoGrinder or Freezer Mill!  Don’t forget Spex offers elemental standards for almost the entire periodic table including the most popular single-element standards for heavy metals.