We discuss the annular electron confinement on the liquid helium surface induced by a submerged tubular electrode. For a shallow liquid layer the resulting potential has a minimum off the symmetry axis of the electrode. The ground-state angular momentum transitions that are driven by the external magnetic field can be resolved when the confinement radii in the first and second Rydberg subbands of the vertical quantization are different, e.g., for submersion depth of the tube comparable to its radius. Then, discontinuities in the main microwave absorption line appear with the period that corresponds to the subsequent magnetic flux quanta passing across the area within the ground-state confinement radius.

中文翻译：

---

液氦上电子的环形限制

我们讨论了由浸没管状电极引起的液氦表面上的环形电子限制。对于浅液层，所得电位在电极对称轴外具有最小值。当垂直量化的第一和第二里德堡子带中的限制半径不同时，例如，管的浸没深度与其半径相当时，可以解决由外部磁场驱动的基态角动量跃迁。然后，主微波吸收线中的不连续性出现，其周期对应于穿过基态限制半径内的区域的后续磁通量量子。