And when we define that as r being equal to zero, essentially we're multiplying the probability density by zero.

当我们定义ｒ等于０处，事实上是把概率密度乘以０．

麻省理工公开课 - 化学原理课程节选

And one common way to think about it, is to think about the value of r, or the radius, below which 90% of that electron density is going to be contained.

而通常的想法，是想象，r，的值，也就是半径的值，即有百分之九十的电子密度,都落在这个范围之内。

麻省理工公开课 - 化学原理课程节选

a perfectly spherical shell dr at some distance, thickness, d r, dr we talk about it as 4 pi r squared d r, so we just multiply that by the probability density.

在某个地方的完美球型壳层,厚度，我们把它叫做4πr平方，我们仅仅是把它,乘以概率密度。

麻省理工公开课 - 化学原理课程节选