And when we look at this, it's actually split by what's called a nodal plane, which is pointed out in light orange here on this picture, but what we just mean is that there is this whole plane that separates the two lobes where there is absolutely no electron density.

我们来看这里，实际上它被一个节面分开，在这图里用淡黄色表示，这意味着这个分开,两个叶瓣的平面上,是完全没有电子密度的。

麻省理工公开课 - 化学原理课程节选

Our picture now is going to be some particle that's traveling in the x-y plane.

我们现在的情景是在 x-y 平面内,运动的质点

耶鲁公开课 - 基础物理课程节选