An electron spectrometer is a device used to perform different forms of

electron spectroscopy Electron spectroscopy refers to a group formed by techniques based on the analysis of the energies of emitted electrons such as photoelectrons and Auger electrons. This group includes X-ray photoelectron spectroscopy (XPS), which also known as El ...

and

electron microscopy An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a ...

. This requires analyzing the energy of an incoming beam of electrons. Most electron spectrometers use a hemispherical electron energy analyzer in which the beam of electrons is bent with electric or magnetic fields. Higher energy electrons will be bent less by the beam, this produces a spatially distributed range of energies. Electron spectrometers are used on a range of scientific equipment, including

particle accelerator A particle accelerator is a machine that uses electromagnetic fields to propel electric charge, charged particles to very high speeds and energies, and to contain them in well-defined particle beam, beams. Large accelerators are used for fun ...

transmission electron microscope Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a gr ...

s, and astronomical satellites.

Types

Electron spectrometers may determine electron energy based on

time of flight Time of flight (ToF) is the measurement of the time taken by an object, particle or wave (be it acoustic, electromagnetic, etc.) to travel a distance through a medium. This information can then be used to measure velocity or path length, or as a w ...

, retarding potential (effectively a

high-pass filter A high-pass filter (HPF) is an electronic filter that passes signals with a frequency higher than a certain cutoff frequency and attenuates signals with frequencies lower than the cutoff frequency. The amount of attenuation for each frequenc ...

), resonant collision or curvature in a deflecting field (magnetic or electric). An electrostatic electron spectrometer uses the electric field, which cause electrons to move along field gradients, whereas magnetic devices cause electrons to move at right angles to the field. Magnetic fields will act in a direction perpendicular to the electron propagation, thereby conserving velocity, whereas electrostatic fields will cause electrons to move along the field gradient, which may change electron energies if the component of the direction of propagation and field gradients are not perpendicular. Owing to these effects, sector based designs are commonly used in electron spectrometers.

Construction

The

effective potential The effective potential (also known as effective potential energy) combines multiple, perhaps opposing, effects into a single potential. In its basic form, it is the sum of the 'opposing' centrifugal potential energy with the potential energy of a ...

in the solution of motion in a magnetic or electric system with rotational symmetry leads to radial focusing onto a mean radius. By superposition of a quadrupole field axial focusing is possible while weakening the radial focusing, until the

astigmatism Astigmatism is a type of refractive error due to rotational asymmetry in the eye's refractive power. This results in distorted or blurred vision at any distance. Other symptoms can include eyestrain, headaches, and trouble driving at ni ...

vanishes. By breaking the rotational symmetry a bit and varying the electrostatic potential along the mean path of the

spherical aberration In optics, spherical aberration (SA) is a type of aberration found in optical systems that have elements with spherical surfaces. Lenses and curved mirrors are prime examples, because this shape is easier to manufacture. Light rays that strike a ...

is minimized. All the electrons from an isotopic source may be sucked off and focused into a directed beam (much like in an

electron gun An electron gun (also called electron emitter) is an electrical component in some vacuum tubes that produces a narrow, collimated electron beam that has a precise kinetic energy. The largest use is in cathode-ray tubes (CRTs), used in nearl ...

), which can then be analyzed. The spectrometer can use entrance and exit slits or use a small source, which only emits into specific angle and a small detector.

Photoelectron The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid stat ...

spectra from single crystals exhibit a dependency on the emission angle, and the entrance slit is needed at the entrance of the hemispherical electron analyzer in

angle-resolved photoemission spectroscopy Angle-resolved photoemission spectroscopy (ARPES) is an experimental technique used in condensed matter physics to probe the allowed energies and momenta of the electrons in a material, usually a crystalline solid. It is based on the photoele ...

and related techniques. There, a position sensitive detector detects the energy along one direction and depending on the additional

optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultra ...

lateral resolution or one angle along the other direction. Electrostatic spectrometers preserve the spin, which can be resolved afterwards.

References

Electron beam Spectrometers Electron spectroscopy {{Spectroscopy-stub

Types

Construction

See also

References