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Encyclopedia > Electromagnetic spectroscopy

Electromagnetic spectroscopy a.k.a. spectrophotometry is the spectroscopy of electromagnetic spectra which arise out of atoms absorbing and emitting quanta of electromagnetic radiation. Extremely high resolution spectrum of the Sun showing thousands of elemental absorption lines (fraunhofer lines) Spectroscopy is the study of spectra, that is, the dependence of physical quantities on frequency. ... Legend: γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves: EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultrahigh frequency VHF = Very high frequency HF = High frequency... Properties An atom (Greek άτομον from ά: non and τομον: divisible) is a submicroscopic structure found in all ordinary matter. ... Electromagnetic radiation can be conceptualized as a self propagating transverse oscillating wave of electric and magnetic fields. ...


Electromagnetic spectroscopy involves the use of a spectrophotometer. In physics, spectrophotometry is the quantitative study of spectra. ...

Contents


Types of electromagnetic radiation measured

This can be in any range of wavelengths: The wavelength is the distance between repeating units of a wave pattern. ...

Electromagnetic spectroscopy can be classified into narrower fields as discussed below, though in some spectroscopic techniques, several processes may be happening at the same time. This page is about the radiation; for the appliance, see microwave oven. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ... IR spectrum of a thin film of liquid ethanol. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... Ultraviolet-Visible Spectroscopy or Ultraviolet-Visible Spectrophotometry (UV/ VIS) involves the spectroscopy of photons (spectrophotometry). ... Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of the visible region, but longer than that of soft X-rays. ... Ultraviolet-Visible Spectroscopy or Ultraviolet-Visible Spectrophotometry (UV/ VIS) involves the spectroscopy of photons (spectrophotometry). ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz...


Types of electromagnetic spectroscopy

Emission spectroscopy

Emission spectroscopy is the study of electromagnetic radiation spectra given off by atoms or molecules that undergo a transition to a lower energy level. Such a process is called fluorescence or, under certain conditions, phosphorescence. Generally, emission spectroscopy deals with visible light and shorter wavelengths, since fluorescence is less likely to happen with long wavelengths. See also: spontaneous emission. A quantum mechanical system can only be in certain states, so that only certain energy levels are possible. ... Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ... Phosphorescent powder under visible light, ultraviolet light, and total darkness. ... Spontaneous emission is the process by which a molecule in an excited state drops to the ground state, resulting in the creation of a photon. ...


Examples:

Fluorescence spectroscopy or fluorometry is a type of electromagnetic spectroscopy used for analyzing fluorescent spectra. ... Flame Emission Spectroscopy (FES) is a form of emission spectroscopy in which energy is provided to a sample through use of a flame. ... In X-ray fluorescence (XRF) a material is exposed to X-rays with a relatively high energy. ... High resolution spectrum of the Sun showing thousands of elemental absorption lines (fraunhofer lines). ...

Absorption spectroscopy

Absorption spectroscopy is the study of electromagnetic radiation spectra absorbed by atoms or molecules that change energy levels. Often, it is used as an analytical technique; specific chemical compounds have a specific absorption spectrum that acts as a fingerprint. Moreover, the amount of absorption is related to the amount of absorbing compound. Absorption spectroscopy can be used to determine the concentration of chemical compounds in samples (see molar absorptivity). Absorption spectroscopy is an analytical tool used by chemists. ... An energy level is a quantified stable energy, which a physical system can have; the term is most commonly used in reference to the electron configuration of electrons, in atoms or molecules. ... In analytical chemistry, the molar absorptivity or extinction coefficient ε of a chemical species at a given wavelength is a measure of how strongly the species absorbs light at that wavelength. ...


Examples of absorption spectroscopy:

Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ... IR spectrum of a thin film of liquid ethanol. ... Atomic absorption spectroscopy in analytical chemistry is a technique for determining the concentration of a particular metal element within a sample. ... Ultraviolet-Visible Spectroscopy or Ultraviolet-Visible Spectrophotometry (UV/ VIS) involves the spectroscopy of photons (spectrophotometry). ... Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of the visible region, but longer than that of soft X-rays. ... Mössbauer spectroscopy is a spectroscopic technique based on the Mössbauer effect. ...

Other techniques

Electromagnetic radiation can interact with matter in ways other than simple absorption and emission, such as in the following techniques:

  • Circular dichroism spectroscopy - measures effects of a sample on the polarization of light.
  • Magnetic circular dichroism
  • Nuclear magnetic resonance (NMR) - measures the resonant absorption of radiofrequency radiation by nuclei in a strong magnetic field. Absorption peaks correspond to transitions in the nuclear spin states of the sample molecule(s).
  • Electron spin resonance - similar to NMR, but looking at electrons.
  • Raman spectroscopy - A molecule can absorb a part of the energy of a photon, which results in a change in frequency (or wavelength) of the photon. The amount of absorbed energy corresponds to an infrared transition in the molecule, even though the photon might have a visible-light wavelength.
  • Stark spectroscopy - measures effects of electrical fields on the spectra.

Circular dichroism, or CD, is defined as the differential absorption of left and right hand circularly polarized light. ... Magnetically induced circular dichroism (MCD), is the differential absorption of left and right circularly polarized light in the presence of a magnetic field. ... Pacific Northwest National Laboratorys high magnetic field (800 MHz) NMR spectrometer being loaded with a sample. ... Current flowing through a wire produces a magnetic field (M) around the wire. ... Electron Paramagnetic Resonance (EPR) or Electron Spin Resonance (ESR) is a spectroscopic technique which detects species that have unpaired electrons, generally meaning that it must be a free radical, if it is an organic molecule, or that it has transition metal ions if it is an inorganic complex. ... Raman spectroscopy is a spectroscopic technique used in condensed matter physics and chemistry to study vibrational, rotational, and other low-frequency modes in a system. ... Stark spectroscopy or electroabsorption spectroscopy is a form of UV/Vis spectroscopy, where the sample is exposed to a strong electrical field. ...

Examples

The spectrum of sunlight

Matter reflects, absorbs or scatters regions of the electromagnetic radiation shown upon it. Depending on the Correlated Color Temperature of the light source, you will perceive the object to be of a differing color. Man has attempted to utilize Plank's Law to assign a specific Correlated Color temperature to each light source sold in your store. Each bulb measured, was assigned a Correlated Color Temperature CCT in kelvins; 2800 K is a living room light, 6000 K is a bright sunny day. "Correlated" is used because all is compared back to a perfect black body radiator. White light is commonly described by its color temperature. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ...


The higher the temperature, the shorter (and bluer) the average visible wavelength. The sun, which has a temperature around 6000 K, emits most strongly in the visible light. However, certain wavelengths are missing from the solar spectrum, which is the result of chemical elements in the chromosphere of the sun that have resonant transitions at those wavelengths. From the exact wavelengths of these missing parts of the spectrum, or absorption lines, we can deduce which elements are present in the sun. The fact that these elements have absorbed the radiation indicates that the chromosphere is cooler than the photosphere. A chemical element, often called simply element, is a chemical substance that canot be divided or changed into other chemical substances by any ordinary chemical technique. ... The chromosphere (literally, color sphere) is a thin layer of the Suns atmosphere just above the photosphere, roughly 10,000 kilometers deep. ... The Sun (or Sol) is the star at the center of our Solar system. ...


However absorption spectra can not give us information about the abundance of the various elements. This is because hydrogen and helium (the main constituents of the sun) need much more energy to excite them enough to absorb radiation than other elements (such as calcium) present. So even though H and He are more abundant, a much smaller percentage of them get excited enough to produce a high intensity. To get a better understanding of abundance of these elements it is necessary to study the emission spectrum of elements in the chromosphere. It is only possible to assess this when the photosphoric radiation is totally obscured during an eclipse. At this time the emission spectrum of the chromosphere is highly dominated by hydrogen, which is the main constituent of the sun. General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Atomic mass 4. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... A materials emission spectrum is the amount of electromagnetic radiation of each frequency it emits when it is heated (or more generally when it is excited). ... Photo taken during the French 1999 eclipse An eclipse (Greek verb: ecleipo, to cease existing or calypse, to cover ) is an astronomical event that occurs when one celestial object moves into the shadow of another. ...


Absorption in the atmosphere

The material in Earth's atmosphere absorbs some of the sunlight passing through it. This has been measured at sea level and various altitudes. Estimates were made of the likely spectrum of sunlight above the atmosphere and the absorption within the atmosphere. Actual measurements above the atmosphere required spacecraft which were able to take such readings. These efforts are illustrated in the following images. Layers of Atmosphere (NOAA) Earths atmosphere is a layer of gases surrounding the planet Earth and retained by the Earths gravity. ...

External links

  • The Science of Spectroscopy - supported by NASA, includes OpenSpectrum, a Wiki-based learning tool for spectroscopy that anyone can edit

  Results from FactBites:
 
Electromagnetic spectroscopy - Wikipedia, the free encyclopedia (852 words)
Electromagnetic spectroscopy involves the use of a spectrophotometer.
Emission spectroscopy is the study of electromagnetic radiation spectra given off by atoms or molecules that undergo a transition to a lower energy level.
Mossbauer spectroscopy - Measures the absorption of gamma rays by atoms bound in a solid as a function of gamma-ray energy.
  More results at FactBites »

 
 

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