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

Question

Quizplus · Accepted Answer

The 21-cm radio emission in hydrogen gas is produced by the inversion of the electron spin relative to the proton spin, from parallel to antiparallel. This is a hyperfine transition in atomic hydrogen.

What Atomic Transition Occurs in the Atoms of Hydrogen Gas