Linear ion traps and quadrupole mass spectrometers play vital roles in quantum technologies and classical mass spectrometry respectively. Therefore, such systems with nearly same operational principles, are very well studied both theoretically and experimentally. Despite such vast knowledge base, linear ion traps continue to be an important research topic, particularly the effect of small perturbations from ideal conditions. Here, non-degenerate nonlinear resonances of the ion dynamics in a linear three-segmented round-rod radio-frequency ion trap have been studied. Purposefully designed perturbation from an ideal 4-rod symmetric structure results in additional instabilities in the dynamics of the trapped ions. The weightage of the dodecapole potential increases by an order of magnitude in such an asymmetric setup compared to that present in usual symmetric setup of nearly equivalent geometry. The experimental results are corroborated by ion dynamics simulations with commercial software SIMION. Increased dodecapole potential in the asymmetric structure leads to resolution of the frequency of ion oscillation in two mutually perpendicular direction in the radial plane which is otherwise unresolved in a symmetric structure in absence of dc potential. Such asymmetric linear trap, in principle, finds importance in the study of Coulomb crystal, mass spectrometry and relevant trapped ion dynamics. It also opens up the possibility to remove undesired ion species (often known as dark ion) within a chain of physical qubits.

中文翻译：

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圆杆几何形状的不对称线性离子阱中的非简并十二极共振

线性离子阱和四极质谱仪分别在量子技术和经典质谱分析中发挥着至关重要的作用。因此，这些具有几乎相同工作原理的系统在理论上和实验上都得到了很好的研究。尽管有如此庞大的知识基础，线性离子阱仍然是一个重要的研究课题，特别是理想条件下小扰动的影响。在这里，研究了线性三段圆杆射频离子阱中离子动力学的非简并非线性共振。理想的 4 杆对称结构特意设计的扰动会导致捕获离子动力学的额外不稳定性。与几乎等效几何形状的通常对称设置中存在的十二极势的权重相比，在这种不对称设置中，十二极势的权重增加了一个数量级。实验结果通过商业软件SIMION的离子动力学模拟得到证实。不对称结构中增加的十二极电势导致径向平面中两个相互垂直方向上的离子振荡频率的分辨率，否则在缺乏直流电势的对称结构中无法解决。原则上，这种不对称线性陷阱在库仑晶体、质谱和相关捕获离子动力学的研究中具有重要意义。它还提供了去除物理量子位链中不需要的离子种类（通常称为暗离子）的可能性。