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In physics and chemistry, the Lyman series is a hydrogen spectral series of transitions and resulting ultraviolet emission lines of the hydrogen atom as an electron goes from n ≥ 2 to n = 1 (where n is the principal quantum number), the lowest energy level of the electron (groundstate).
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]
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 .
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.
At even higher field strengths, comparable to the strength of the atom's internal field, the electron coupling is disturbed and the spectral lines rearrange. This is called the Paschen–Back effect. In modern scientific literature, these terms are rarely used, with a tendency to use just the "Zeeman effect".
A hydrogen molecule can absorb a far-ultraviolet photon (11.2 eV < energy of the photon < 13.6 eV) and make a transition from the ground electronic state X to excited state B (Lyman) or C (Werner). Radiative decay occurs rapidly. 10–15% of the decays occur into the vibrational continuum. This means that the hydrogen molecule has dissociated.
The hydrogen line is produced when an electron in a neutral hydrogen atom is excited to the triplet spin state, or de-excited as the electron and proton spins go to the singlet state. The energy difference between these two hyperfine states is 5.9 × 10 − 6 {\displaystyle 5.9\times 10^{-6}} electron volts , with a wavelength of 21 centimeters.
The one-electron states with even are even under parity, while those with odd are odd under parity. Hence hydrogen-like atoms with n>1 show first-order Stark effect. The first-order Stark effect occurs in rotational transitions of symmetric top molecules (but not for linear and asymmetric molecules). In first approximation a molecule may be ...