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Lyman-alpha, typically denoted by Ly-α, is a spectral line of hydrogen (or, more generally, of any one-electron atom) in the Lyman series. It is emitted when the atomic electron transitions from an n = 2 orbital to the ground state ( n = 1), where n is the principal quantum number .
The Lyman-alpha forest was first discovered in 1970 by astronomer Roger Lynds in an observation of the quasar 4C 05.34. [1] Quasar 4C 05.34 was the farthest object observed to that date, and Lynds noted an unusually large number of absorption lines in its spectrum and suggested that most of the absorption lines were all due to the same Lyman-alpha transition. [2]
The transitions are named sequentially by Greek letters: from n = 2 to n = 1 is called Lyman-alpha, 3 to 1 is Lyman-beta, 4 to 1 is Lyman-gamma, and so on. The series is named after its discoverer, Theodore Lyman. The greater the difference in the principal quantum numbers, the higher the energy of the electromagnetic emission.
Animation of a Lyman-alpha blob. The giant Lyman-alpha blob LAB-1 (left) and an artist's impression of what it might look like if viewed from relatively close (right). In astronomy, a Lyman-alpha blob (LAB) is a huge concentration of a gas emitting the Lyman-alpha emission line. LABs are some of the largest known individual objects in the Universe.
Reproduction of an early electron microscope constructed by Ernst Ruska in the 1930s. Many developments laid the groundwork of the electron optics used in microscopes. [2] One significant step was the work of Hertz in 1883 [3] who made a cathode-ray tube with electrostatic and magnetic deflection, demonstrating manipulation of the direction of an electron beam.
In the Bohr model, the Lyman series includes the lines emitted by transitions of the electron from an outer orbit of quantum number n > 1 to the 1st orbit of quantum number n' = 1. The series is named after its discoverer, Theodore Lyman , who discovered the spectral lines from 1906–1914.