Search results
Results from the WOW.Com Content Network
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.
The strongest hydroxyl radical spectral line radiates at 18 centimeters, and atomic hydrogen at 21 centimeters (the hydrogen line). These two molecules, which combine to form water , are widespread in interstellar gas , which means this gas tends to absorb radio noise at these frequencies.
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.
Electromagnetic – the hyperfine transition of hydrogen, also known as the hydrogen line or 21 cm line 2.4 GHz: Electromagnetic – microwave ovens, wireless LANs and cordless phones (starting in 1998) 2.6–3.8 GHz: A common desktop CPU speed as of 2014 5.8 GHz: Electromagnetic – cordless telephone frequency introduced in 2003 10 10: 10 GHz
In principle, any emission line can be used to make intensity maps if it can be detected. Other emission lines that have been proposed as cosmological tracers include: Rotational transitions in molecules, such as carbon monoxide [13] Fine structure transitions from species such as ionized carbon [14] Lyman-alpha emission from hydrogen [15]
The amount of energy needed to reverse the spin of the electron is equivalent to a photon at the frequency of 1.420 405 751 768 GHz, [1] which corresponds to the 21 cm line in the hydrogen spectrum. Hydrogen masers are very complex devices and sell for as much as US$235,000. [2] There are two types to be distinguished: active and passive.
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 "visible" hydrogen emission spectrum lines in the Balmer series. H-alpha is the red line at the right. Four lines (counting from the right) are formally in the visible range. Lines five and six can be seen with the naked eye, but are considered to be ultraviolet as they have wavelengths less than 400 nm.