In
physics
Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...
, an atomic mirror is a device which
reflects neutral
atoms
Atoms are the basic particles of the chemical elements. An atom consists of a nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished from each other ...
in a way similar to the way a conventional mirror reflects
visible light
Light, visible light, or visible radiation is electromagnetic radiation that can be perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm ...
. Atomic mirrors can be made of
electric field
An electric field (sometimes called E-field) is a field (physics), physical field that surrounds electrically charged particles such as electrons. In classical electromagnetism, the electric field of a single charge (or group of charges) descri ...
s or
magnetic field
A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...
s,
electromagnetic wave
In physics, electromagnetic radiation (EMR) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space. It encompasses a broad spectrum, classified by frequency or its inverse, wavelength, ...
s
or just
silicon wafer
In electronics, a wafer (also called a slice or substrate) is a thin slice of semiconductor, such as a crystalline silicon (c-Si, silicium), used for the fabrication of integrated circuits and, in photovoltaics, to manufacture solar cells.
The ...
; in the last case, atoms are reflected by the attracting tails of the van der Waals attraction (see
quantum reflection).
[
] Such reflection is efficient when the normal component of the wavenumber of the atoms is small or comparable to the effective depth of the attraction potential (roughly, the distance at which the potential becomes comparable to the kinetic energy of the atom). To reduce the normal component, most atomic mirrors are blazed at the
grazing incidence.
At grazing incidence, the efficiency of the
quantum reflection can be enhanced by a surface covered with ridges (
ridged mirror).
[
]
The set of narrow ridges reduces the
van der Waals attraction of atoms to the surfaces and enhances the reflection. Each ridge blocks part of the wavefront, causing
Fresnel diffraction
In optics, the Fresnel diffraction equation for near-field diffraction is an approximation of the Kirchhoff's diffraction formula, Kirchhoff–Fresnel diffraction that can be applied to the propagation of waves in the near and far field, near fi ...
.
Such a mirror can be interpreted in terms of the
Zeno effect.
We may assume that the atom is "absorbed" or "measured" at the ridges. Frequent measuring (narrowly spaced ridges) suppresses the transition of the particle to the half-space with absorbers, causing
specular reflection
Specular reflection, or regular reflection, is the mirror-like reflection (physics), reflection of waves, such as light, from a surface.
The law of reflection states that a reflected ray (optics), ray of light emerges from the reflecting surf ...
. At large separation
between thin ridges, the reflectivity of the
ridged mirror is determined by dimensionless momentum
, and does not depend on the origin of the wave; therefore, it is suitable for reflection of atoms.
Applications
*Atomic
interferometry
Interferometry is a technique which uses the ''interference (wave propagation), interference'' of Superposition principle, superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important inves ...
See also
*
Quantum reflection
*
Ridged mirror
*
Zeno effect
*
Atomic nanoscope
*
Atom laser
An atom laser is a coherent state of propagating atoms. They are created out of a Bose–Einstein condensate of atoms that are output coupled using various techniques. Much like an optical laser, an atom laser is a coherent beam that behaves lik ...
References
{{reflist
Atomic, molecular, and optical physics