Enhancement of intersubband transition probability in a one-dimensional constriction

We find that the angular distribution of electrons injected through a quantized one-dimensional constriction exhibits fine structure at 300 mK which is smeared out at 1.5 K. The relative sizes of the peaks in the fine structure can be changed by modifying the potential in the injector constriction. Using a simple model, we show that the results are consistent with modulation of the intersubband transition probabilities, which are highly sensitive to the asymmetry of the constriction.