 Following Bohr, one can label the difference between the \(n'\) stationary state and the \(n''\) stationary state by \(\tau\); that is, if the electron jumps to the nearest stationary state, \(\tau = 1\); if it jumps two stationary states away, \(\tau = 2\); and so on. Although according to the classical definition \(\tau\) specifies a particular harmonic component of the classical motion, according to the quantum mechanical definition \(\tau\) specifies the change in the quantum number in a particular jump.