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# Brackett series

[brak-it]
In atomic physics, the Brackett series is one of several series of spectral lines produced by hydrogen. The series is named after the American physicist Frederick Sumner Brackett who first observed the spectral lines in 1922.

The lines appear in emission when hydrogen atoms' electrons descend to the fourth energy level from a higher level, and they appear in absorption when the electrons ascends from the fourth energy level to higher levels. These lines lie in the infrared part of the electromagnetic spectrum, with wavelengths ranging from 4.05 micrometres (Brackett-alpha) to 1.46 micrometres (the series limit).

 $n$ Wavelength (nm) 5 6 7 8 9 $infty$ 4052.5 2625.9 2166.1 1945.1 1818.1 1458.0

## References

• Frederick Sumner Brackett, "Visible and infra-red radiation of hydrogen"; Astrophysical Journal, vol. 56, (1922) p.154;