Astrophysics (index)about

state of ionization

(difference in an ion's electron count versus proton count)

An ion is an atom that has more or less electrons than protons or a neutral atom, in which they match, and the term state of ionization (or, more briefly, just ionization) is used to characterize this difference, e.g., "missing two electrons". The term is also used regarding the degree to which this is true of a material (collection of atoms/ions, e.g., what percent is ionized and/or how many electrons are missing) or simply to assert that an atom is ionized.

For a collection of atoms, e.g., a gas, the percentages of the gas at each state of ionization is of interest, because of its relation to temperature and to the production of the spectral lines, allowing the study of spectral lines to be used to determine temperature, through the Saha equation.

In astronomy, the following terminology is often used: the chemical symbol followed by I means neutral, II means singly ionized, III for doubly ionized, etc., e.g., CI, CII, CIII for carbon at these three states of ionization. The more common symbol in other sciences is (e.g., for hydrogen), H+ for singly ionized, H++ for doubly ionized, etc.

(physics,quantum mechanics,atoms,ionization)

Referenced by:
Advanced Composition Explorer (ACE)
anomalous cosmic rays (ACR)
Balmer jump
binding energy
calcium (Ca)
carbon (C)
carbonate system
ionized carbon fine structure line ([CII])
cold gas
continuum emission
diffractive interstellar scintillation (DISS)
energetic neutral atom (ENA)
epoch of reionization (EOR)
star formation feedback
fine structure
forbidden line
galactic electron density
Gunn-Peterson trough
molecular hydrogen dissociation front (H2 dissociation front)
ionized hydrogen (HII)
HI region (HI)
ionization correction factor (ICF)
instability strip
ionization potential
interstellar medium (ISM)
Kramers opacity law
Lorentz force
mass spectrometer
Millimeter-wave Intensity Mapping Experiment (mmIME)
magnetorotational instability (MRI)
nitrogen (N)
nitrite (NO2-)
oscillator strength
partial ionization zone
plasma frequency
planetary nebula (PN)
protoplanetary disk (PPD)
refractive interstellar scintillation (RISS)
Saha equation
solar energetic particle (SEP)
star formation rate (SFR)
supernova (SN)
spectral line
Strömgren sphere
sulfur (S)
surface gravity
Thomson optical depth
Tomographic Ionized-carbon Mapping Experiment (TIME)
Wilson-Bappu effect