Remes Philip M, Glish Gary L
Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA.
J Phys Chem A. 2009 Apr 16;113(15):3447-54. doi: 10.1021/jp808955w.
Infrared multiphoton dissociation (IRMPD) combined with ion trajectory simulations has been used to obtain probability maps of ion position as a function of different operating parameters in a quadrupole ion trap mass spectrometer. The factors that contribute to the depth of the pseudopotential trapping well are analyzed, and their effects on the efficiency of IRMPD are demonstrated. Ion trajectory simulations are used to substantiate experimental results and demonstrate in greater detail the dynamic nature of the ion population's positional distribution. In particular, it is shown that the so-called "q(z) value" used during photodissociation can be of great consequence, as can the frequency of ac trapping voltage applied to the ring electrode. The results reveal that parameters which increase the pseudopotential well have the effect of decreasing the size of the ion cloud and maximizing overlap between the irradiating laser and the ions. Thus, while the common understanding of IRMPD dictates otherwise, IRMPD fragmentation efficiencies really depend on many ion trap operating parameters, much as collision-induced dissociation does.
红外多光子解离（IRMPD）与离子轨迹模拟相结合，已被用于在四极离子阱质谱仪中获取离子位置概率图，该概率图是不同操作参数的函数。分析了对赝势阱深度有贡献的因素，并展示了它们对IRMPD效率的影响。离子轨迹模拟用于证实实验结果，并更详细地展示离子群体位置分布的动态性质。特别地，结果表明光解离过程中使用的所谓“q(z)值”以及施加到环形电极的交流捕获电压频率都可能产生重大影响。结果表明，增加赝势阱的参数会减小离子云的尺寸，并使照射激光与离子之间的重叠最大化。因此，尽管对IRMPD的通常理解并非如此，但IRMPD碎片化效率实际上取决于许多离子阱操作参数，就像碰撞诱导解离一样。
