In Dirac's notation, an expression which is a → scalar product of the dual vectors → bra and → ket which describe a quantum state. The bra vector appears on the left of the ket vector.
From M.Fr. braguette "codpiece armor."
Fr.: série de Brackette
A series of lines in the infrared spectrum of atomic hydrogen due to electron jumps between the fourth and higher energy levels (Br α has wavelength 4.052 μm, Br γ 2.166 μm).
Named after the American physicist Frederick Brackett (1896-1980); → series.