Yeah, we'd expect to see a single bond in hydrogen.

嗯，我们预计在氢分子里会看到一个单键。

麻省理工公开课 - 化学原理课程节选

But in sigma orbitals, you have no nodal planes along the bond axis, so if we had a nodal plane here, we'd see an area where the wave function was equal to zero.

但在sigma轨道里，沿着轴向是没有节点平面的，如果我们有个节点，我们就会看到某个地方波函数等于0。

麻省理工公开课 - 化学原理课程节选