Generalized oscillator strength density from an initial atomic state nl to final states n＇l＇ or ∈＇l＇ forming a final channel is a function of the energy transfer ∈ and the momentum transfer q. We report our study on the nodal curves in the ∈-q plane, where the matrix element for the generalized oscillator strength density vanishes. For high momentum transfer, the positions of the nodal curves can be obtained by scaling the hydrogenic results. For low momentum transfer, the nodal curves depend strongly on the difference of the quantum defects △μ of the initial and final channels; the topology of the nodal curves for △μ>0 is completely different from the topology for △μ<0.