Contenido

El mecanismo por el cual la materia emite radiación electromagnética es el dominio de la espectroscopia. La radiación electromagnética se atribuye a las diferencias de energía en las transiciones de los electrones de unos niveles atómicos a otros. La espectroscopia se relaciona en la mayoría de los casos con la tercera interacción. Estudia en qué frecuencia o longitud de onda una sustancia puede absorber o emitir energía en forma de un cuanto de luz.

La energía de un fotón (un cuanto de luz")) de una onda electromagnética o su correspondiente frecuencia equivale a la diferencia de energía entre dos estados cuánticos de la sustancia estudiada:.

donde es la constante de Planck, es la frecuencia del haz de luz u onda electromagnética asociada a ese cuanto de luz y es la diferencia de energía. Esta ecuación es conocida también como la ecuación básica de la espectroscopia. Las diferencias de energía entre estados cuánticos dependen de la composición elemental de la prueba o de la estructura de la molécula, y por eso este método proporciona información importante para astrónomos, físicos, químicos y biólogos.

Por medio de un espectrofotómetro se mide el espectro de la luz (intensidad de la luz absorbida, reflejada o emitida en función de la frecuencia o de la longitud de onda). Los espectros se diferencian considerablemente de elemento a elemento.

Definition of "spectrum"

In general, the distribution of intensity as a function of frequency or wavelength is called "spectrum."

In addition to visible light, spectroscopy today covers a large part of the electromagnetic spectrum.

Spectroscopy objective

The goal of spectroscopy is to obtain information about a test or a radiating body. For example:.

The stars, as well as interstellar matter, emit electromagnetic waves; Astronomers have come to know everything we know about the extraterrestrial environment by deciphering the messages that these waves carry when they reach our planet. It should be noted that the emission and subsequent modifications experienced by these radiations are the result of many factors: the elemental composition of the source that emits them, temperature, pressure and degree of ionization at which it is found, influence of magnetic and electric fields, etc. On the other hand, as astronomers and physicists have reproduced these different states of matter in their laboratories and obtained the corresponding spectra, these serve as standards that allow the spectra of celestial bodies to be analyzed and all the information they contain to be extracted. In the case of light spectra, the studies constitute spectral analysis, which specifically consists of the study of light previously decomposed into monochromatic radiation using a prism or a diffraction grating.

On the other hand, the orbitals of the atom of a chemical element are as characteristic of it as the fingerprints of an individual, and always different from those of any other element. This is how physicists have been able to catalog the set of luminous radiations that each of the elements emits when it is in a state of incandescence.

The light we receive from a star, for example, consists of a mixture of radiation, some of which comes from atoms of hydrogen, helium, iron, etc. If this light is passed through a slit to obtain a long and narrow beam, and if it passes through a prism "Prism (optics)"), the different radiations will be classified, since the prism deflects those with the longest wavelength to one end (corresponding to red light) and those with the shortest wavelength to the other (violet light); Between both extremes the waves of intermediate length will be arranged: orange, yellow, green, blue and indigo. In short, this results in a continuous spectrum whose appearance is that of a narrow transverse rainbow stripe.

Another phenomenon intervenes between the emission of this spectrum by the atoms excited by the heat of the star and its reception on Earth, which is what allows spectral analysis. Every time an emitted radiation encounters, during its propagation in the same atmosphere of the star, a vapor "Vapor (state)") containing atoms of the same element, it is absorbed by one of these. Consequently, in the spectrum of that star that will be obtained on Earth, each of the positions corresponding to the intercepted wavelengths will be devoid of light and a dark line will appear. Thus, instead of the emission spectrum, an absorption spectrum will be obtained that will contain in the form of lines the traces of all the chemical elements existing in the star.

In addition to indicating the elemental composition of the light source and the physical state of its matter, the spectrum reveals whether the luminous body and the Earth are approaching or moving away from each other, in addition to indicating the relative speed at which they do so (Doppler-Fizeau effect).

In the spectrum of stars there is always an area of ​​radiation that is more intense than the others. This preponderance is independent of the chemical composition of the star and results from its surface temperature. We know from experience that, if a metal is heated progressively, it begins to have a dark red incandescence that becomes increasingly lighter and ends up giving off a white light. Thus, red stars are less hot than orange ones, and these are less hot than yellow ones, and so on. Using the spectra, astronomers have been able to determine the surface temperature of stars and classify them into groups (Hertzsprung-Russell diagram).

On the other hand, when comparing the lines of the spectrum of a star with those of terrestrial light, it is observed that in the stellar spectrum the lines are slightly shifted towards the red end of the spectrum or towards the color violet. This phenomenon, due to the Doppler-Fizeau effect, allows us to calculate the radial velocity with which the star is moving away from or approaching the Earth. In particular, it has made it possible to discover that all galaxies are moving away from each other, which is proof of the expansion of the universe.

Finally, thanks to spectral analysis, helium was discovered in 1868 after identifying the lines obtained in a spectrum after a solar eclipse took place. Since then, spectral analysis of celestial bodies has revealed that they are all composed of the elements we know on Earth and that appear in Mendeleev's periodic table.

The main phenomena used are:

These phenomena can lead to intervention:[10]​.

The following table presents an illustration of the different spectroscopy techniques depending on the wavelength domain.

Spectroscopy is a technique widely used in astronomy, mainly in UV, optics and infrared. It is distinguished:

Contenido

El mecanismo por el cual la materia emite radiación electromagnética es el dominio de la espectroscopia. La radiación electromagnética se atribuye a las diferencias de energía en las transiciones de los electrones de unos niveles atómicos a otros. La espectroscopia se relaciona en la mayoría de los casos con la tercera interacción. Estudia en qué frecuencia o longitud de onda una sustancia puede absorber o emitir energía en forma de un cuanto de luz.

La energía de un fotón (un cuanto de luz")) de una onda electromagnética o su correspondiente frecuencia equivale a la diferencia de energía entre dos estados cuánticos de la sustancia estudiada:.

donde es la constante de Planck, es la frecuencia del haz de luz u onda electromagnética asociada a ese cuanto de luz y es la diferencia de energía. Esta ecuación es conocida también como la ecuación básica de la espectroscopia. Las diferencias de energía entre estados cuánticos dependen de la composición elemental de la prueba o de la estructura de la molécula, y por eso este método proporciona información importante para astrónomos, físicos, químicos y biólogos.

Por medio de un espectrofotómetro se mide el espectro de la luz (intensidad de la luz absorbida, reflejada o emitida en función de la frecuencia o de la longitud de onda). Los espectros se diferencian considerablemente de elemento a elemento.

Definition of "spectrum"

In general, the distribution of intensity as a function of frequency or wavelength is called "spectrum."

In addition to visible light, spectroscopy today covers a large part of the electromagnetic spectrum.

Spectroscopy objective

The goal of spectroscopy is to obtain information about a test or a radiating body. For example:.

The stars, as well as interstellar matter, emit electromagnetic waves; Astronomers have come to know everything we know about the extraterrestrial environment by deciphering the messages that these waves carry when they reach our planet. It should be noted that the emission and subsequent modifications experienced by these radiations are the result of many factors: the elemental composition of the source that emits them, temperature, pressure and degree of ionization at which it is found, influence of magnetic and electric fields, etc. On the other hand, as astronomers and physicists have reproduced these different states of matter in their laboratories and obtained the corresponding spectra, these serve as standards that allow the spectra of celestial bodies to be analyzed and all the information they contain to be extracted. In the case of light spectra, the studies constitute spectral analysis, which specifically consists of the study of light previously decomposed into monochromatic radiation using a prism or a diffraction grating.

On the other hand, the orbitals of the atom of a chemical element are as characteristic of it as the fingerprints of an individual, and always different from those of any other element. This is how physicists have been able to catalog the set of luminous radiations that each of the elements emits when it is in a state of incandescence.

The light we receive from a star, for example, consists of a mixture of radiation, some of which comes from atoms of hydrogen, helium, iron, etc. If this light is passed through a slit to obtain a long and narrow beam, and if it passes through a prism "Prism (optics)"), the different radiations will be classified, since the prism deflects those with the longest wavelength to one end (corresponding to red light) and those with the shortest wavelength to the other (violet light); Between both extremes the waves of intermediate length will be arranged: orange, yellow, green, blue and indigo. In short, this results in a continuous spectrum whose appearance is that of a narrow transverse rainbow stripe.

Another phenomenon intervenes between the emission of this spectrum by the atoms excited by the heat of the star and its reception on Earth, which is what allows spectral analysis. Every time an emitted radiation encounters, during its propagation in the same atmosphere of the star, a vapor "Vapor (state)") containing atoms of the same element, it is absorbed by one of these. Consequently, in the spectrum of that star that will be obtained on Earth, each of the positions corresponding to the intercepted wavelengths will be devoid of light and a dark line will appear. Thus, instead of the emission spectrum, an absorption spectrum will be obtained that will contain in the form of lines the traces of all the chemical elements existing in the star.

In addition to indicating the elemental composition of the light source and the physical state of its matter, the spectrum reveals whether the luminous body and the Earth are approaching or moving away from each other, in addition to indicating the relative speed at which they do so (Doppler-Fizeau effect).

In the spectrum of stars there is always an area of ​​radiation that is more intense than the others. This preponderance is independent of the chemical composition of the star and results from its surface temperature. We know from experience that, if a metal is heated progressively, it begins to have a dark red incandescence that becomes increasingly lighter and ends up giving off a white light. Thus, red stars are less hot than orange ones, and these are less hot than yellow ones, and so on. Using the spectra, astronomers have been able to determine the surface temperature of stars and classify them into groups (Hertzsprung-Russell diagram).

On the other hand, when comparing the lines of the spectrum of a star with those of terrestrial light, it is observed that in the stellar spectrum the lines are slightly shifted towards the red end of the spectrum or towards the color violet. This phenomenon, due to the Doppler-Fizeau effect, allows us to calculate the radial velocity with which the star is moving away from or approaching the Earth. In particular, it has made it possible to discover that all galaxies are moving away from each other, which is proof of the expansion of the universe.

Finally, thanks to spectral analysis, helium was discovered in 1868 after identifying the lines obtained in a spectrum after a solar eclipse took place. Since then, spectral analysis of celestial bodies has revealed that they are all composed of the elements we know on Earth and that appear in Mendeleev's periodic table.

The main phenomena used are:

These phenomena can lead to intervention:[10]​.

The following table presents an illustration of the different spectroscopy techniques depending on the wavelength domain.

Spectroscopy is a technique widely used in astronomy, mainly in UV, optics and infrared. It is distinguished: