|MadSci Network: Chemistry|
The term "high energy electron" is a relative term. It is used to denote the energy state of an electron within an atom that has acquired enough energy to move to the next “energy level” within the atom. If you picture the nucleus of an atom and the electron clouds located at various distances from the nucleus, each of these electron clouds have their own “energy level” since the electrons of which these clouds are made of need to have enough energy to remain at a given distance from the nucleus. Remember that the nucleus is where the positive charge of the atom is located, while the electrons are negatively charged. If you add energy to the atom, in the form of say light, this energy, if it has the right frequency, may excite electrons in one of the electron clouds and give them enough energy for them to become “high energy” electrons and move into the next level up. If the energy is of the right frequency they can also leave the atom, leaving behind a positively charged atom, what we call a cation.
Think of sodium -- if you add enough energy to a sodium atom in the gas phase, one of its electrons can leave the atom as a “high energy” electron leaving the positively charged sodium cation ( Na + Energy = Na+ + e-).
Another use of the phrase “high energy electrons” is when electrons are produced by for example bombarding an atom of a given element with high energy atoms of another element, causing the emission of “high energy electrons”. This can also be achieved by heating the element under special conditions resulting on a sputtering of electrons. This the basis for the so-called electron guns.
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