Balmer series
(H)
(hydrogen lines for electrons settling from n > 2 to n = 2)
The Balmer series is the set of
hydrogen spectral lines emitted
when an electron descends from
an electron shell number n greater than 2 down to n = 2,
or the analogous absorption lines when absorbed electromagnetic radiation
makes the electron do the opposite.
It is one of the hydrogen line series, such as
the Lyman series and is
named after Johann Balmer.
Lines:
 3 > 2: Halpha, Hα, 656.3 nm (red)
 4 > 2: Hbeta, Hβ, 486.1 nm (cyan)
 5 > 2: Hgamma, Hγ, 434.1 nm (blue)
 6 > 2: Hdelta, Hδ, 410.2 nm (violet)
 7 > 2: Hepsilon, Hε, 397.0 nm (ultraviolet)
 8 > 2: Hzeta, Hζ, 388.9 nm (ultraviolet)
 9 > 2: Heta, Hη, 383.5 nm (ultraviolet)
 ...
 infinity > 2: 364.6 nm (ultraviolet, the Balmer limit).
Formula for the wavelengths:
wavelength = Balmer's constant × n² / ( n²4 )
where
 wavelength  within the Balmer series.
 Balmer's constant = 3.6450682 × 10^{7} m or 364.50682 nm (same as 4/R_{H} where R_{H} is the Rydberg constant for hydrogen).
 n is the higher electron shell number.
The Balmer series, especially Hα is used
to determine the redshift of quasars and
distant galaxies because it is often prominent.
(Balmer,hydrogen,line series,lines,spectrum)
Further reading:
http://en.wikipedia.org/wiki/Balmer_series
WaveL  Freq  Photon Energy   
364nm  824THz  3.5eV  begin  Balmer series 
656nm  457THz  1.9eV  end  Balmer series 

Referenced by pages:
Balmer jump
Balmerbreak galaxy (BBG)
Be star
Bohr model
Brackett series
emission line galaxy (ELG)
emission nebula
Halpha (Ha)
HII region (HII)
hydrogen (H)
hyperfine structure
Lyman series (L)
Paschen series
quasar (QSO)
star formation rate (SFR)
shell star (sh)
spectral line energy distribution (SLED)
spectral line
spectral line designation
Index