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ucph>Tommy at 13:40, 26 August 2019

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The neutron is a nuclear particle with a mass, \(m_{\rm n}\), rather close to that of the proton<ref name="chadwick32">J. Chadwick, Possible existence of a neutron, ''Nature'', vol. 129, p. 312-312 (1932)</ref>

\begin{equation}\label{dummy782923085}
m_{\rm n} = 1.67493 \cdot 10^{-27} \, {\rm \,kg} .
\end{equation}

The neutron does not exist naturally in free form, but decays into a proton, an electron, and an anti-neutrino. The neutron lifetime, \(\tau = 886 {\rm \,s}\)<ref name="lifetime">A. Garcia, J.L. Garcia-Luna and G.L. Castro, <i>Phys. Lett. B</i>, vol. 500, p. 66 (2001)</ref>, is much longer than the time a neutron spends within a scattering experiment, which is merely a fraction of a second. Hence, neutron decay can typically be neglected in experiments.

The neutron is electrically neutral but still possesses a magnetic moment

\begin{equation}\label{eq:intro_moment}
\mu = \gamma \mu_{\rm N} ,\,
\end{equation}

where \(\gamma= - 1.91304\) is the neutron magnetogyric ratio and the nuclear magneton is given by \(\mu_{\rm N} = e \hbar / (2 m_{\rm p}) = 5.05078 \cdot 10^{-27} \,{\rm J}/{\rm T}\). The neutron magnetic moment is coupled antiparallel to its spin, which has the value \(s=1/2\).

The neutron interacts with nuclei via the strong nuclear force and with magnetic moments via the electromagnetic force. Most of this text deals with the consequences of these interactions; i.e. the scattering and absorption of neutrons by atoms and nuclei inside materials, as well as reflection from surfaces and interfaces.

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Basic properties of the neutron - Revision history

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ucph>Tommy at 13:40, 26 August 2019