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Aspectrometer (/spɛkˈtrɒmɪtər/) is a scientific instrument used to separate and measurespectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where the spectral components are somehow mixed. Invisible light a spectrometer can separate whitelight and measure individual narrow bands of color, called a spectrum. Amass spectrometer measures the spectrum of the masses of the atoms or molecules present in a gas. The first spectrometers were used to split light into an array of separate colors. Spectrometers weredeveloped in early studies ofphysics,astronomy, andchemistry. The capability ofspectroscopy to determinechemical composition drove its advancement and continues to be one of its primary uses. Spectrometers are used inastronomy to analyze the chemical composition ofstars andplanets, and spectrometers gather data on theorigin of the universe.
Examples of spectrometers are devices that separateparticles,atoms, andmolecules by theirmass,momentum, orenergy. These types of spectrometers are used inchemical analysis andparticle physics.[1]
Optical spectrometers (often simply called "spectrometers"), in particular, show the intensity oflight as a function of wavelength or of frequency. The different wavelengths of light are separated byrefraction in aprism or bydiffraction by adiffraction grating.Ultraviolet–visible spectroscopy is an example.
These spectrometers utilize the phenomenon ofoptical dispersion. The light from a source can consist of acontinuous spectrum, anemission spectrum (bright lines), or anabsorption spectrum (dark lines). Because each element leaves itsspectral signature in the pattern of lines observed, aspectral analysis can reveal the composition of the object being analyzed.[2]
A spectrometer that is calibrated for measurement of the incident optical power is called aspectroradiometer.[3]
Optical emission spectrometers (often called "OES or spark discharge spectrometers"), are used to evaluatemetals to determine the chemical composition with very high accuracy. A spark is applied through a high voltage on the surface which vaporizes particles into a plasma. The particles and ions then emit radiation that is measured by detectors (photomultiplier tubes) at different characteristic wavelengths.[4]
As protons, electrons, and many other nuclei have a netmagnetic moment they interact with an applied external magnetic field. This can be used for high resolution liquidnuclear magnetic resonance spectroscopy, in which the unique magnetic environment of the nucleus changes according to electrons around them, yielding information on the chemical composition of the sample. Likewise, unpaired electrons interact with magnetic fields, yielding the technique ofelectron paramagnetic resonance.
Some forms of spectroscopy involve analysis of electron energy rather than photon energy.X-ray photoelectron spectroscopy is an example.[5]
Amass spectrometer is an analytical instrument that is used to identify the amount and type of chemicals present in a sample by measuring themass-to-charge ratio and abundance of gas-phaseions.[6]
The energy spectrum of particles of known mass can also be measured by determining the time of flight between twodetectors (and hence, the velocity) in atime-of-flight spectrometer. Alternatively, if the particle-energy is known, masses can be determined in atime-of-flight mass spectrometer.
When a fastcharged particle (chargeq, massm) enters a constant magnetic fieldB at right angles, it is deflected into a circular path of radiusr, due to theLorentz force. The momentump of the particle is then given by
wherem andv are mass and velocity of the particle.[7] The focusing principle of the oldest and simplest magnetic spectrometer, the semicircular spectrometer,[8][9] invented by J. K. Danisz, is shown on the left. A constant magnetic field is perpendicular to the page. Charged particles of momentump that pass the slit are deflected into circular paths of radiusr = p/qB. It turns out that they all hit the horizontal line at nearly the same place, the focus; here a particle counter should be placed. VaryingB, this makes possible to measure the energy spectrum ofalpha particles in an alpha particle spectrometer, ofbeta particles in a beta particle spectrometer,[10] of particles (e.g., fastions) in a particle spectrometer, or to measure the relative content of the various masses in amass spectrometer.
Since Danysz' time, many types of magnetic spectrometers more complicated than the semicircular type have been devised.[10]
Generally, theresolution of an instrument tells us how well two close-lying energies (or wavelengths, or frequencies, or masses) can be resolved. Generally, for an instrument with mechanical slits, higher resolution will mean lower intensity.[11]
OpenStax, Astronomy. OpenStax. 13 October 2016. <http://cnx.org/content/col11992/latest/>
| Vibrational (IR) | |||||||
|---|---|---|---|---|---|---|---|
| UV–Vis–NIR "Optical" | |||||||
| X-ray and Gamma ray | |||||||
| Electron | |||||||
| Nucleon | |||||||
| Radiowave | |||||||
| Others |
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| Ion source | |
|---|---|
| Mass analyzer | |
| Detector | |
| MS combination | |
| Fragmentation | |
| International | |
|---|---|
| National | |
