Optical spectroscopy, dealing with electromagnetic radiation (light) in the Ultraviolet, Visible, and Near-infrared ranges, is the measurement of electromagnetic energy intensity as a function of wavelength. We call this optical spectroscopy because techniques in this field employ optical devices to diffuse or focus light. It’s an incredibly versatile science with numerous techniques for gathering useful information from light interacting in the environment.
The right spectroscopy technique depends on the application and what data is required. Spectroscopy techniques are often classified by the nature of the interaction between energy and the material to be sampled. Electromagnetic radiation is produced by oscillating electric and magnetic fields which radiates outward along a linear path at a constant velocity. It is possible to characterize these electromagnetic waves in respect to wavelength, amplitude, frequency, intensity, polarization, and other criteria. When that radiation comes into contact with other matter, the characteristics of that radiation change. By measuring radiation in various experimental circumstances, we gain valuable data.
Several spectroscopy techniques look at the interaction of light and matter at the atomic level. This might involve working with “free atoms” such as in laser-induced breakdown spectroscopy when a laser creates a micro-plume of plasma by ablating a sample surface for elemental analysis. This might also involve light scattering resonances such as a measurement of Raman scattering that enables a view into the atomic structure of a sample.
Read MoreSome materials, when supplied with radiant energy, become "excited" as the electrons orbiting the atoms begin to move faster and expand. Fluorescence occurs when those atoms are excited with ultraviolet radiation and emit light at a longer wavelength, usually within the visible range, to release that energy and return to a ground state. Several minerals and organic compounds fluoresce under ultraviolet light making this a popular spectroscopic technique for many biomedical applications. Fluorescence usually only releases a small fraction, approximately 3%, of the supplied energy in the form of light making this a very demanding spectroscopy technique that requires high sensitivity and long integration times.
Read MoreIrradiance spectroscopy measures the radiant flux (power) striking a unit area of a surface and is used for the characterization of light, often, but not always, sunlight. This spectroscopy technique provides a detailed characterization of a light source with respect to intensity by wavelength.
Solar irradiance is of deep concern in climate studies, astrology, and solar and renewable energy production. This includes everything from testing solar simulators that are used in photovoltaic cell production to coupling to telescopes to study distant astral bodies could be using irradiance spectroscopy techniques.
Laser-induced breakdown spectroscopy (LIBS) is an extremely useful technique for elemental analysis that creates a micro-plasma on the surface of a sample by focusing a short laser pulse at the sample’s surface. Plasma is produced on the surface from laser ablation, which reaches high temperatures that cool rapidly. The light emitted from when plasma cools can be analyzed, and reveals spectral peaks much like a chemical fingerprint.
This technique is widely adopted in several industries and has several compelling advantages over other techniques for elemental analysis.
When light strikes any material, it is either absorbed, transmitted (allowed to pass through), or reflected, or more likely, some combination of these. Absorption and Transmission/ Reflection spectroscopy techniques are, in a sense, opposing techniques.
Absorption spectroscopy measures what has been subtracted (has been absorbed) from the incident light, for example when testing for the presence of a substance known to absorb a certain wavelength of light, if that wavelength is in deed absorbed it may mean the presence of that analyte substance. Furthermore, the rate at which it will absorb light at that wavelength is proportional to the concentration of that substance in the sample. This spectroscopy technique is widely used in analytical chemistry, climate research, and pollution monitoring applications.
Read MoreTransmission and reflection spectroscopy, on the other hand, measures the light that is present after interacting with a sample, either because it has been reflected off of or transmitted through that sample. Whether light is reflected or transmitted, or not, depends on the physical characteristics and properties of the tested material. This method of spectroscopic investigation might be employed in color measurements in art restoration, thin film metrology in the semiconductor industry, or fruit grading and sorting in agriculture.
Read MoreColor Spectroscopy is ideal for obtaining exact wavelengths of color and measuring their values. Many manufacturers need effective color measurement techniques in such fields as paints, dyes, and cosmetics, as well as some agricultural applications. Additionally, the biological sciences use color measurement in many various ways.
Color measurement systems are generally designed to cover the range between 380-780 nm with a spectral resolution around 5 nm (FWHM). Therefore, Avantes offers fast data acquisition spectrometers that allow for high production rates when measuring the color of objects or the color of light from a source.
Near-Infrared or NIR spectroscopy measures light in the infrared. This light exists between 700 and 2500 nm on the electromagnetic spectrum. Because the light at these wavelengths can penetrate material at a deeper level than others, the use of NIR technology is crucial for many biomedical diagnosing applications. Avantes offers our NIRLine which features both cooled and uncooled instruments which allows the user to choose between emphasizing high-sensitivity or low-noise applications.
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