Brackett series
(hydrogen lines for electrons settling from n > 4 to n = 4)
The Brackett series is the set of
emission lines from atomic hydrogen gas,
due to electrons descending from
an electron shell number n greater than 4 down to n = 4,
or the analogous absorption lines when absorbed electromagnetic radiation
makes electrons do the opposite.
It is one of the hydrogen line series, such as
the Lyman series and Balmer series and is
named after Frederick Sumner Brackett.
Lines:
 5 > 4: 4051 nm
 6 > 4: 2625 nm
 7 > 4: 2166 nm
 8 > 4: 1944 nm
 9 > 4: 1817 nm
 ...
 infinity > 4: 1458 nm
Formula for the wavelengths:
1/wavelength = R_{H} ( 1/16  1/n² )
 wavelength is the wavelength within the Brackett series.
 R_{H} is the Rydberg constant for hydrogen, 1.0973731568160 × 10^{7}m^{1} = 13.6eV / hc
 n is the higher electron shell number.
 h  Planck constant.
 c  speed of light in a vacuum.
(Brackett,hydrogen,line series,lines,spectrum)
Further reading:
https://en.wikipedia.org/wiki/Hydrogen_spectral_series
WaveL  Freq  Photon Energy   
1458nm  206THz  850meV  begin  Brackett series 
4050nm  74THz  306meV  end  Brackett series 

Referenced by pages:
hydrogen (H)
spectral line
Index