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debye

A unit of electric dipole moment that has suffered various differing definitions. Symbol, D. The unit is named for P. J. W. Debye (1884–1966).

1

One debye = 10⁻¹⁸ esu centimeter or about 3.336 × 10⁻³⁰ coulomb meters. This value is roughly the magnitude of the electric dipole moment of many molecules.

Apparently Fairbrother¹ was the first to use the term, but Jenkins² uses the unit, giving numerical values as multiples of 10⁻¹⁸ esu, and a few months later Sugden³ gives numerical values without the “× 10⁻¹⁸” saying they are “in the usual units.” So the debye is one of those units that was in use by practitioners before it received a name.

The name probably arose because the values appear as solutions to an equation known as the Debye equation.

1. F. Fairbrother.
Determination of dipole moments in solution. [letter to the editor]
Nature, volume 134, page 458 (1934).

Page 458: “The slopes of these lines yield the following moments in Debye units (D = 1 × 10⁻¹⁸ e.s.u.). ... The average is 4.25 D...”

2. H. O. Jenkins.
Molecular polarizations of nitrobenzene in various solvents at 25 [letter to the editor]
Nature, volume 133, page 106 (January 20, 1934).

3. S. Sugden.
Determination of dipole moments in solution. [letter to the editor]
Nature, volume 133, page 415 (March 17, 1934).

2

Product of the electron charge and the radius of the first Bohr orbit of hydrogen, 2.54 × 10⁻¹⁸ esu cm

3

Product of the electron charge and 1 angstrom, 4.803 × 10⁻¹⁸ esu cm