A sequence of absorption or emission lines in the near-infrared part of the spectrum, due to hydrogen. The Brackett series of lines arises from electron jumps between the fourth energy level and higher levels. The lines have wavelengths from 4.05 μ‎m (Brackett-α‎) towards shorter wavelengths, the spacing between the lines diminishing as they converge on the series limit at 1.46 μ‎m. They are named after the American physicist Frederick Sumner Brackett (1896–1972). See also Hydrogen Spectrum.