debye

The debye ( , ; symbol: D) is a CGS unit (a non-SI metric unit) of electric dipole moment named in honour of the physicist Peter J. W. Debye. Likely the earliest recommendation for the Debye as a unit was in the Physikalisch-chemisches Taschenbuch (physical chemistry handbook) written by Carl Drucker and Erich Proskauer in early 1932. It is defined as statcoulomb-centimetres. Historically the debye was defined as the dipole moment resulting from two charges of opposite sign but an equal magnitude of 10−10 statcoulomb (generally called e.s.u. (electrostatic unit) in older scientific literature), which were separated by 1 ångström. This gave a convenient unit for molecular dipole moments. {| |- |height=30|1 D ||= 10−18 statC·cm |- |height=30| |= 10−18 cm5/2⋅g1/2⋅s−1 |- |height=30| |= 10−10 statC·Å |- |height=30| |≘  C·m |- |height=30| |≈ |- |height=30| |≈ |- |height=30| |≈ |- |height=30| |≈ |- |}

Typical dipole moments for simple diatomic molecules are in the range of 0 to 11 D. Molecules with symmetry point groups or containing inversion symmetry do not have a permanent dipole moment, while highly ionic molecular species have a very large dipole moment, e.g. gas-phase potassium bromide, KBr, with a dipole moment of 10.41 D. A proton and an electron 1 Å apart have a dipole moment of 4.8 D.