# Difference between revisions of "Dipole moment"

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(1A x 1 e = 4.8D, a convenient rule) |
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For molecular systems, it is customarily given in units of Debyes, after the physicist [[Peter J. W. Debye]]. | For molecular systems, it is customarily given in units of Debyes, after the physicist [[Peter J. W. Debye]]. | ||

− | In SI units, <math>1</math>D equals approximately <math>3.33564\times 10^{-30}</math> Coulomb-meter (exactly <math>10^{-21}</math>C m<math>^2</math>/s divided by <math>c</math>, the speed of light in vacuum). Conversely, 1 C m = <math>2.9979 10^{29}</math>D. | + | In SI units, <math>1</math>D equals approximately <math>3.33564\times 10^{-30}</math> Coulomb-meter (exactly <math>10^{-21}</math>C m<math>^2</math>/s divided by <math>c</math>, the speed of light in vacuum). Conversely, 1 C m = <math>2.9979 10^{29}</math>D. This is unit is convenient for molecular systems since 1<math>\AA \times 1 e=4.803</math>D. |

## Revision as of 11:27, 26 May 2008

The **electric dipole moment** is a measure of polarity. It is the second term in a multipole expansion of a field (the first one being the monopole, or Coulombic, term.) Its definition, for a system of point charges, is

For molecular systems, it is customarily given in units of Debyes, after the physicist Peter J. W. Debye. In SI units, D equals approximately Coulomb-meter (exactly C m/s divided by , the speed of light in vacuum). Conversely, 1 C m = D. This is unit is convenient for molecular systems since 1D.