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 is produced by a spin -flip transition, which means the direction of the electron's spin is …

Dec 8, 2022 · In fact, it’s the narrowest, most precise transition line known in all of atomic and nuclear physics! This map of the Milky Way, in red, maps out the neutral hydrogen in 21 centimeter emissions.

21-centimetre radiation, electromagnetic radiation of radio wavelength emitted by cold, neutral, interstellar hydrogen atoms. The hydrogen atom is composed of a positively charged particle, the proton, and a negatively charged particle, the electron. These particles have some intrinsic angular momentum called spin.

We explore some applications of the 21-cm neutral hydrogen line in astrophysics. From observa-tions in a narrow band around 21 cm we find estimates for the peak temperature of the chromosphere of the sun, as well as the angular extent of a portion of the galactic plane around l …

We discuss the properties of the 21 cm hydrogen H1 line based on the numerical calculations. The magnitude of the hyperfine interaction depends only on the probability of the ground state hydrogen at the origin. So the s- electron with zero orbital angular momentum.

The observation of the 21cm line of hydrogen marked the birth of spectral-line radio astronomy. It was first observed in 1951 by Harold Ewen and Edward M. Purcell at Harvard, followed soon afterward by observers in Holland and Australia.

The 21-cm line is the triplet-to singlet hyper ne transition of atomic hydrogen ground state due to the interaction of the magnetic moments of the proton and the electron.

Jul 16, 2010 · The Hydrogen 21-cm line of radiation is the emission of radio energy from atomic Hydrogen throughout the galaxy when the atom transitions from its first excited state to its ground state. This transition arises due to the spin-spin interaction …

5 days ago · It was the first radio spectral line to be discovered, in 1951, and has proved invaluable in mapping the distribution and motions of hydrogen clouds in our Galaxy and others. The 21-cm line is caused by electrons in the ground …

Since the presence of a spectral line, whose true frequency is known, permits to measure the movements of the gas clouds via the Doppler effect, the 21 cm line has been of immense value to study the motions of gas in our own galaxy as well as in other galaxies.