Francis William Aston, inventor of the mass spectrometer and discoverer of isotopes

(September 1, 1877 in Birmingham (United Kingdom) – November 20, 1945 in London)

Francis Aston_Cientificos

In 1903 he obtained a scholarship to study at the University of Birmingham and six years later he was a collaborator at the Cavendish Laboratory at the University of Cambridge, invited by Joseph John Thomson, where he worked on the identification of the isotopes of neon and investigated electric discharges in neon. low pressure tubes.

After the First World War, in 1919, he invented the mass spectrograph that allowed him to discover 212 of the 287 isotopes of isotopes of non-radioactive elements and for which he would receive the Nobel Prize in Chemistry in 1922. The mass spectrograph is an experimental device which allows charged particles to be separated according to their mass. Furthermore, he established a rule, named after him, that states that odd-numbered atomic elements cannot have more than two stable isotopes.

In his early investigations with the mass spectrograph, Aston discovered that when a sample of pure neon gas was passed through the instrument, two separate spots formed on the detector, meaning that the gas contained atoms corresponding to two different masses. Therefore, he interpreted his discovery to indicate the existence of two different types of neon atoms and that both must have the same number of protons, since all forms of neon always contain the same number of protons, but a different number of protons. neutrons. As a consequence, their atomic masses must have been different.

With his research, Aston provided the first experimental proof of the existence of isotopes, that is, of forms of the same atom with an equal number of protons, but with a different number of neutrons, and reflected it in two publications: "Isotopes" (1922) and "Mass Spectrometers and Isotopes" (1933).

Later he was a professor at Trinity College, Cambridge and, in 1921, he entered the Royal Society. In 1935 he was elected president of the International Atomic Committee.

After the First World War he invented a mass spectrometer that allowed him to discover, due to differences in mass, a certain number of isotopes in non-radioactive elements, which allowed him to identify 212 of the 287 natural isotopes. This was the reason why he was awarded the Nobel Prize.

Francis Aston died on November 20, 1945 in London.

Foundation of Mass Spectrometry

Mass spectrometry is based on a simple principle: when a flow of charged particles is subjected to the action of a magnetic field, it undergoes a deflection; the amplitude of said deviation depends on the mass and the charge of the particles that make up the flow.

Espectrómetro de masas (Real)

The spectrometer or mass spectrograph essentially consists of three parts: the ionization chamber, the deflection chamber, and the detector. In the ionization chamber, the atoms of the substance to be identified receive an excitation energy that makes them lose electrons. Sometimes this energy is achieved simply by heating the sample. As a consequence of the loss of electrons, atoms become positively charged particles called ions.

The ions produced in the ionization chamber then pass into the diversion chamber which is subjected to a strong magnetic field. When the flow of positive ions crosses the chamber, the trajectory of each of them undergoes a deviation due to the effect of the magnetic field; instead of going through the camera in a straight line, they do so following a curve. The degree of curvature of each path depends on the mass and charge of the positive ion; the heavy ions follow a path that does not deviate much from the straight line, while the lighter ones are more deviated.

Leaving the deflection chamber, the positive ions collide with a photographic plate, or similar element, installed in the detector. The detector records the magnitude of the deviations from the straight line experienced by the trajectories of the particles that make up the sample, thus indicating the mass and charge of said particles. Since each element and each atom have a characteristic mass and charge, reading the record collected by the detector allows the atoms present in the sample to be identified.

It currently has multiple applications by allowing the masses of the particles that are part of a sample to be determined with the aim of identifying them. For example, it is used to identify traces of substances found in places where a crime has been committed, when the quantities found are too small to be identified.

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