continuous spectrum

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continuous spectrum

A spectrum consisting of a continuous region of emitted or absorbed radiation in which no discrete lines are resolvable. The emission from hot fairly dense matter will produce a continuous spectrum, as with the continuous emission of ultraviolet, visible, and infrared radiation from the Sun's photosphere. Synchrotron emission is another example of continuous emission.

Spectrum, Continuous


a spectrum of electromagnetic radiation in which the energy distribution is characterized by a continuous function Φ(v) of the radiation frequency or by a continuous function Φ(v.) of the radiation wavelength. For a continuous spectrum, Φ(v) or f (ʎ) varies slightly over a broad range of v or ʎ. By contrast, in line and band spectra Φ(v) has, at discrete values of the frequency v = v1, v2, v3, . . ., pronounced maxima that are very narrow for spectral lines and broader for spectral bands. When radiation in the optical region is decomposed into a spectrum by spectroscopic instruments, a continuous spectrum is obtained in the form of a continuous band (when the spectrum is visually observed or photographically recorded) or a smooth curve (when the spectrum is photoelectrically recorded). Continuous spectra are observed both in emission and in absorption. The equilibrium spectrum is an example of a continuous spectrum encompassing the entire range of frequencies and characterized by a definite spectral energy distribution. The equilibrium spectrum is characterized by Planck’s radiation law.

Superpositions of a line spectrum on a continuous spectrum are possible in some cases. For example, in solar and stellar spectra both a discrete absorption spectrum (Fraunhofer lines) and a discrete emission spectrum (in particular, the spectral emission lines of the hydrogen atom) may be superposed on a continuous emission spectrum.

According to quantum theory, a continuous spectrum arises when quantum transitions occur between two sets of energy levels; at least one of the sets must belong to a continuous sequence of levels—that is, to a continuous energy spectrum. An example is the continuous spectrum of the hydrogen atom resulting from bound-free transitions. In such transitions, electrons move from discrete energy levels with different values of the quantum number n to the continuous set of energy levels lying above the ionization limit. In absorption, a continuous spectrum corresponds to the ionization of a H atom—that is, to electronic transitions from a bound state to a free state. In emission, a continuous spectrum corresponds to the recombination of an electron and a proton—that is, to electronic transitions from a free state to a bound state. Free-free transitions also occur; they are transitions between different pairs of energy levels belonging to a continuous set of energy levels. The continuous spectra resulting from such transitions correspond to bremsstrahlung in the case of emission and to the reverse process in the case of absorption. Bound-bound transitions, on the other hand, give rise to a line spectrum; such transitions occur between different pairs of discrete energy levels.

Continuous spectra can be obtained for nonmonatomic molecules as a result of the superposition of a very large number of spectral lines of finite width when transitions occur between sets of discrete energy levels that are close to each other. Apparent continuous spectra may be obtained when the spectroscopic instruments used have insufficient resolving power. In this case, a line or band spectral structure merges into a continuous spectrum.


continuous spectrum

[kən¦tin·yə·wəs ′spek·trəm]
The portion of the spectrum of a linear operator which is a continuum.
A radiation spectrum which is continuously distributed over a frequency region without being broken up into lines or bands.
References in periodicals archive ?
The weak continuous spectrum of the chromosphere [1518] has drawn the attention of solar observers for over 100 years [19-22].
Therefore, scattering by relativistic electrons does not need to be invoked to account for the presence of a continuous spectrum in the K-corona devoid of Fraunhofer lines.
In traditional civilizations there was a continuous spectrum of creation which was always related to God, from the making of a simple comb to the composition of f poetry and everything in between; everything was related to God and reflected His quality as the Supreme Artisan on the human plane.
Rydberg spectral lines of an atom are sometimes superimposed on the continuous spectrum of a different configuration.
In addition to these considerations, observation of this case of mixed morphology suggests that granular cell tumors could form a continuous spectrum of lesions, initially represented by a reactive/hyperplastic process that subsequently may acquire truly neoplastic potential.
Autism itself runs a continuous spectrum based on the functioning of the individual, from autism (lower functioning) to Asperger's syndrome (later onset, less severe speech deficit).
Scoring: Keep in mind cynicism, skepticism and optimism all exist on a continuous spectrum.
Most recently, a review of data taken by ROSAT's extreme-ultraviolet camera has revealed that the X rays form a continuous spectrum over a broad range of energies.
A continuous spectrum is not needed; therefore, the spectrometer that provides the absorbance data can be relatively simple.
It will be obvious from the foregoing that there are no clear boundaries between these three recognized classes of petroleum wax, and that a continuous spectrum exists, ranging from the lowest melting point simplest paraffin wax of almost 100% alkane content to the somewhat higher melting point and vastly more complex microcrystalline wax containing almost 100% branched chain iso alkane or `non normal' high molecular weight hydrocarbons.
Vice President and practice director Dominique Bonte comments: "It is essential the ITS debate shifts to encompass the wider framework of the connected car environment which offers a nearly continuous spectrum of connectivity options offering a variety of range, line of sight, and response time characteristics.

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