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A hydrogen atom with proton and electron spins aligned (top) undergoes a flip of the electron spin, resulting in emission of a photon with a 21 cm wavelength (bottom) The hydrogen line, 21 centimeter line, or H I line [a] is a spectral line that is created by a change in the energy state of solitary, electrically neutral hydrogen atoms.
It will capture a detailed radio image of the sky in the range of 1420 MHz. The first stars ionized the gas around them, which produced a specific pattern of ionization. PasT detects the brightness of the 21 cm hydrogen line at redshift from 6 to 25. This hydrogen cosmic background radiation disappears on ionization, allowing the study of large ...
In its most common variant, 21 cm intensity mapping, the 21cm emission line of neutral hydrogen is used to trace the gas. The hydrogen follows fluctuations in the underlying cosmic density field, with regions of higher density giving rise to a higher intensity of emission.
English: Ground state hyperfine levels of hydrogen (parallel and antiparallel) with the spin-flip transition, emitting radiation at 1420 MHz. The corresponding wavelength is 21 cm. (21-cm line, hydrogen line)
For example, the 2 → 1 line is called "Lyman-alpha" (Ly-α), while the 7 → 3 line is called "Paschen-delta" (Pa-δ). Energy level diagram of electrons in hydrogen atom. There are emission lines from hydrogen that fall outside of these series, such as the 21 cm line.
Here, the electric quadrupole interaction is due to the 14 N-nucleus, the hyperfine nuclear spin-spin splitting is from the magnetic coupling between nitrogen, 14 N (I N = 1), and hydrogen, 1 H (I H = 1 ⁄ 2), and a hydrogen spin-rotation interaction due to the 1 H-nucleus. These contributing interactions to the hyperfine structure in the ...
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This is accomplished by looking at the 21-cm line emission produced by hot diffuse neutral hydrogen from distant galaxy clusters and from the intracluster medium. [1] This neutral hydrogen traces out the large scale structures in the universe, and so can be used to map out the large scale Baryon Acoustic Oscillation (BAO) structure of the universe.