Photosphere:
* Hydrogen atoms: Primarily absorb photons in the Balmer series, producing the characteristic absorption lines seen in the solar spectrum.
* Other elements: Elements like sodium, calcium, magnesium, and iron also contribute to absorption in the photosphere, creating their own spectral lines.
Chromosphere:
* Hydrogen atoms: Still play a crucial role, absorbing photons in the Lyman series, leading to the emission of ultraviolet radiation.
* Helium atoms: Contribute to absorption in the chromosphere, especially in the far ultraviolet.
* Ions: Ions of various elements, including those mentioned above, also contribute to absorption in the chromosphere.
Corona:
* Ions: Highly ionized atoms of elements like iron, nickel, and calcium are responsible for absorbing photons in the corona. The extremely high temperature of the corona leads to these atoms being highly ionized.
* Free electrons: Free electrons contribute to the absorption of photons in the corona through the phenomenon of Thomson scattering.
Key Factors:
* Temperature: The temperature of each layer dictates the ionization state of the atoms, affecting the absorption lines produced.
* Composition: The relative abundance of elements in the star plays a role in the overall absorption spectrum.
* Photon Energy: The energy of the photons being absorbed determines which transitions are possible in the atoms, and therefore which spectral lines are produced.
Example:
In the Sun's photosphere, hydrogen atoms absorb photons in the Balmer series, producing the characteristic absorption lines seen in the solar spectrum. These lines are visible because the photosphere is cool enough for hydrogen atoms to exist in their ground state, allowing them to absorb photons and jump to higher energy levels.
Remember that this is a general overview, and the specific details of absorption in different layers will vary depending on the particular star.
