The debye (symbol: D) (; ) is a
CGS unit (a non-
SI metric unit) of
electric dipole moment[Two equal and opposite charges separated by some distance constitute an electric dipole. This dipole possesses an electric dipole moment whose value is given as charge times length of separation, it is a vector whose direction is in the direction of the unit vector of the position vector of the positive charge w.r.t negative charge:
:p = ''q''r.] named in honour of the physicist
Peter J. W. Debye. It is defined as
statcoulomb
The franklin (Fr) or statcoulomb (statC) electrostatic unit of charge (esu) is the physical unit for electrical charge used in the cgs-esu and Gaussian units. It is a derived unit given by
: 1 statC = 1 dyn1/2⋅cm = 1 cm3/2⋅g1/2⋅s−1.
Tha ...
-
centimeter
330px, Different lengths as in respect to the Electromagnetic spectrum, measured by the Metre and its deriveds scales. The Microwave are in-between 1 meter to 1 millimeter.
A centimetre (international spelling) or centimeter (American spellin ...
s.
[The statcoulomb is also known as the franklin or electrostatic unit of charge.
:1 statC = 1 Fr = 1 esu = 1 cm3/2⋅g1/2⋅s−1.] Historically the debye was defined as the dipole moment resulting from two charges of opposite sign but an equal magnitude of 10
−10 statcoulomb
[10−10 statcoulomb corresponds to approximately 0.2083 units of elementary charge.] (generally called e.s.u. (electrostatic unit) in older scientific literature), which were separated by 1
ångström
The angstromEntry "angstrom" in the Oxford online dictionary. Retrieved on 2019-03-02 from https://en.oxforddictionaries.com/definition/angstrom.Entry "angstrom" in the Merriam-Webster online dictionary. Retrieved on 2019-03-02 from https://www.m ...
.
[The ångström is within an order of magnitude of the nuclear separation for a typical covalent bond.
:1 Å = 100 pm = 10−8 cm = 10−10 m.] This gave a convenient unit for molecular dipole moments.
:
Typical dipole moments for simple diatomic molecules are in the range of 0 to 11 D. Symmetric homoatomic species, e.g.
chlorine
Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...
, Cl
2, have zero dipole moment, and 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.
[''Physical chemistry'' 2nd Edition (1966) G. M. Barrow. McGraw-Hill.]
The debye is still used in
atomic physics and
chemistry because SI units have until recently been inconveniently large. The smallest SI unit of electric dipole moment is the quectocoulomb-metre, which corresponds to roughly 0.3 D.
[With a value of 10−30, quecto- is the smallest SI prefix, accepted as an SI prefix by the CGPM on 18 November 2022.]
See also
*
Buckingham (unit) (CGS unit of electric quadrupole)
Notes
References
{{reflist
Non-SI metric units
Peter Debye
Centimetre–gram–second system of units