What atomic transition occurs in atoms of hydrogen gas in the galactic spiral arms to produce 21-cm radio emission? A) The change in the vibrational state of the H atoms in the H₂ molecule B) The transition from the n = 2 to n = 1 level in atomic hydrogen C) The inversion of the electron spin relative to the proton spin,from parallel to anti-parallel D) The change in rotation about an axis perpendicular to the molecular axis in the molecule H₂

Question

Quizplus · Accepted Answer

The 21-cm radio emission in hydrogen gas is produced by the transition involving the flip of the electron spin from being parallel to the proton spin to being anti-parallel. This is a hyperfine transition within the ground state of atomic hydrogen.

What Atomic Transition Occurs in Atoms of Hydrogen Gas in the Galactic