Astrophysics (Index)About

state of ionization

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

An ion is an atom or molecule that has more or less electrons than protons, as opposed to a neutral atom in which the numbers match. The term state of ionization (or, more briefly, just ionization) is used to characterize this surplus or deficit, such as +2 for "missing two electrons". In context, the term may also mean the degree of ionization, referring to a number of atoms, characterizing how many are ions and how many are at each state. For a collection of atoms/molecules, 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)
Further reading:

Referenced by pages:
anomalous cosmic rays (ACR)
air shower
Auger effect
Balmer jump (BJ)
binding energy
Boltzmann equation
calcium (Ca)
carbon (C)
ionized carbon fine structure line ([CII])
cold gas
continuum emission
cooling function
degree of ionization
diffractive interstellar scintillation (DISS)
electrostatic barrier
energetic neutral atom (ENA)
epoch of reionization (EOR)
electron volt (eV)
star formation feedback
fine structure
forbidden line
Fraunhofer lines
galactic electron density
molecular hydrogen dissociation front (H2 dissociation front)
helium 1083 nm line
HII region (HII)
HI region (HI)
ionization correction factor (ICF)
instability strip
ion engine
ionization fraction
ionization potential
ionizing radiation
iron (Fe)
interstellar medium (ISM)
kappa mechanism (κ-mechanism)
Kramers opacity law
Lorentz force
Lyman-alpha forest
mass spectrometer
Millimeter-wave Intensity Mapping Experiment (mmIME)
magnetorotational instability (MRI)
nitrogen (N)
nitrite (NO2-)
O-type star (O)
oscillator strength
partial ionization zone
plasma astrophysics
plasma frequency
planetary nebula (PN)
protoplanetary nebula (PPN)
protoplanetary disk (PPD)
refractive interstellar scintillation (RISS)
Rydberg unit
Saha equation
star formation rate (SFR)
supernova (SN)
solar storm
spectral class
spectral line
spectral line designation
Strömgren sphere
sulfur (S)
Thomson optical depth (τT)
Tomographic Ionized-carbon Mapping Experiment (TIME)
transition region
Wilson-Bappu effect