We established previously that we can write a wave funciton as a product of two functions T(r,t) = woe-tr. There are several advantages to this form. A stationary state is a wave function that has a probability density that is time independent. (Recall the standing waves on a string we saw in introductory physics.) The second advantage is that states have definite total energy. Recall the classical Hamiltonian H(x, p) = p2 2m + V(x) = E (26)12 2 H = V2 + V (r). (10) 2m