where "n" is the (true) principal quantum number, "l" the azimuthal quantum number, and "f""nl"("r") is an oscillatory polynomial with "n" - "l" - 1 nodes. Slater argued on the basis of previous calculations by Clarence Zener that the presence of radial nodes was not required to obtain a reasonable approximation. He also noted that in the asymptotic limit (far away from the nucleus), his approximate form coincides with the exact hydrogen-like wave function in the presence of a nuclear charge of "Z"-"s" and in the state with a principal quantum number n equal to his effective quantum number "n"*.