In physics, a spectrometer is an apparatus to measure a spectrum.[1] Generally, a spectrum is a graph that shows intensity as a function of wavelength, of frequency, of energy, of momentum, or of mass.
Contents
- 1 Optical spectrometer
- 2 Mass spectrometer
- 3 Time-of-flight spectrometer
- 4 Magnetic spectrometer
- 5 Resolution
- 6 References
Optical spectrometer
Optical spectrometers (often simply called "spectrometers"), in particular, show the intensity of light as a function of wavelength or of frequency. The deflection is produced either by refraction in a prism or by diffraction in a diffraction grating.
Mass spectrometer
A mass spectrometer is an analytical instrument that is used to identify the amount and type of chemicals present in a sample by measuring the mass-to-charge ratio and abundance of gas-phase ions.[2]
Time-of-flight spectrometer
The energy spectrum of particles of known mass can also be measured by determining the time of flight between two detectors (and hence, the velocity) in a time-of-flight spectrometer. Alternatively, if the velocity is known, masses can be determined in a time-of-flight mass spectrometer.
Magnetic spectrometer
A positive charged particle moving in a circle under the influence of the Lorentz force
F
When a fast charged particle (charge q, mass m) enters a constant magnetic field B at right angles, it is deflected into a circular path of radius r, due to the Lorentz force. The momentum p of the particle is then given by
- ,
Focus of a magnetic semicircular spectrometer
where m and v are mass and velocity of the particle. The focussing principle of the oldest and simplest magnetic spectrometer, the semicircular spectrometer,[3] invented by J. K. Danisz, is shown on the left. A constant magnetic field is perpendicular to the page. Charged particles of momentum p that pass the slit are deflected into circular paths of radius r = 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. Varying B, this makes possible to measure the energy spectrum of alpha particles in an alpha particle spectrometer, of beta particles in a beta particle spectrometer,[1] of particles (e.g., fast ions) in a particle spectrometer, or to measure the relative content of the various masses in a mass spectrometer.
Since Danysz' time, many types of magnetic spectrometers more complicated than the semicircular type have been devised.[1]
Resolution
Generally, the resolution 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.[1]
References
- ^ a b c d K. Siegbahn, Alpha-, Beta- and Gamma-Ray Spectroscopy, North-Holland Publishing Co. Amsterdam (1966)
- ^ "mass spectrometer" (PDF). 2009. doi:10.1351/goldbook.M03732.
- ^ Jan Kazimierz Danysz, Le Radium 9, 1 (1912); 10, 4 (1913)
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Spectroscopy
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| Infrared |
- FT-IR
- Raman
- Resonance Raman
- Rotational
- Vibrational
- Rotational-vibrational
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| UV-Vis-NIR |
- Ultraviolet-visible
- Fluorescence
- Vibronic
- Near-infrared
- Resonance enhanced multiphoton ionization (REMPI)
- Laser-induced
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X-ray and
Photoelectron |
- Photoelectron
- Atomic
- Emission
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| Nucleon |
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| Radiowave |
- NMR
- Terahertz
- ESR/EPR
- Ferromagnetic resonance
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| Others |
- Acoustic resonance spectroscopy
- Auger spectroscopy
- Astronomical spectroscopy
- Cavity ring down spectroscopy
- Circular Dichroism spectroscopy
- Coherent anti-Stokes Raman spectroscopy
- Cold vapour atomic fluorescence spectroscopy
- Correlation spectroscopy
- Deep-level transient spectroscopy
- Dual polarisation interferometry
- Electron phenomenological spectroscopy
- EPR spectroscopy
- Force spectroscopy
- Fourier transform spectroscopy
- Hadron spectroscopy
- Hyperspectral imaging
- Inelastic electron tunneling spectroscopy
- Inelastic neutron scattering
- Laser-Induced Breakdown Spectroscopy
- Mössbauer spectroscopy
- Neutron spin echo
- Photoacoustic spectroscopy
- Photoemission spectroscopy
- Photothermal spectroscopy
- Pump-probe spectroscopy
- Raman optical activity spectroscopy
- Raman spectroscopy
- Saturated spectroscopy
- Scanning tunneling spectroscopy
- Spectrophotometry
- Time-resolved spectroscopy
- Time-Stretch
- Thermal infrared spectroscopy
- Video spectroscopy
- Vibrational circular dichroism
- Vibrational spectroscopy of linear molecules
- X-ray photoelectron spectroscopy
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