The ratio of the square of certain concentration gas diffusion depth and diffusion time is constant when it diffuses and reacts through the solids bed.

一定浓度的气体通过固体颗粒层扩散-反应时，其扩散深度的平方与扩散时间的比值为常数。

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This review first summarizes the general theory of spin diffusion in solids, including semi-classical description and the more exact approach, i.

首先介绍固态中自旋扩散的一般理论，包括半经典描述和建立在投影算子理论上的密度矩阵描述。

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