Debye relaxation

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Debye relaxation is the dielectric relaxation response of an ideal, noninteracting population of dipoles to an alternating external electric field. It is usually expressed in the complex permittivity $\varepsilon$ of a medium as a function of the field's frequency $ω$ :

$\hat{\varepsilon}(\omega) = \varepsilon_{\infty} + \frac{\Delta\varepsilon}{1+i\omega\tau},$

where $\varepsilon_{\infty}$ is the permittivity at the high frequency limit, $\Delta\varepsilon = \varepsilon_{s}-\varepsilon_{\infty}$ where $\varepsilon_{s}$ is the static, low frequency permittivity, and $τ$ is the characteristic relaxation time of the medium.