He goes back and redoes the calculation, only in this case he says what I am going to do is I am going to redo the calculation for helium, but I am going to consider not just the mass of the electron but the reduced mass of the system.

他回去重新做了计算，仅在这种情况下他才会说说我将要,为氦重做计算，但我认为,不只是电子的质量,还有系统质量的减少量。

固态化学导论课程节选 : 麻省理工公开课