Collings BA, Douglas DJ
Department of Chemistry, University of British Columbia, Vancouver, Canada.
J Am Soc Mass Spectrom. 2000 Nov;11(11):1016-22. doi: 10.1016/s1044-0305(00)00171-9.
The resonant frequencies for quadrupole excitation of ions confined with a buffer gas in a linear quadrupole ion trap with Mathieu parameters a = 0 and q approximately 0.36 have been measured. The resonances are predicted to occur at angular frequencies omega(K)n given by omega(K)n = (omega/K)n + beta without the presence of a buffer gas where omega is the angular frequency of the trapping radio frequency, K = 1, 2, 3... is the order of the resonance calculated with perturbation theory, and n = 0, +/-1, +/-2, +/-3.... The resonances are measured through fragmentation of protonated reserpine. The observed frequencies agree closely with the theoretical values but there are small differences which vary from +0.6% at K = 2 to -2.7% at K = 6. This is believed to be the result of the dependence of the resonant frequencies upon the buffer gas density and/or the excitation amplitude. The resolution of the resonances (measured from the depletion of precursor and formation of fragment ions) increased by a factor of 2 as K increased from 1 to 6. This increase in resolution warrants further investigation into the use of higher order resonances for isolation and excitation of trapped ions.
已测量了在具有马蒂厄参数a = 0且q约为0.36的线性四极离子阱中，被缓冲气体限制的离子进行四极激发时的共振频率。预计在不存在缓冲气体的情况下，共振会在角频率ω(K)n处发生，其中ω(K)n = (ω/K)n + β，这里ω是捕获射频的角频率，K = 1、2、3……是用微扰理论计算的共振阶数，n = 0、±1、±2、±3……通过质子化利血平的碎片化来测量共振。观测到的频率与理论值非常接近，但存在小的差异，从K = 2时的 +0.6%到K = 6时的 -2.7%不等。这被认为是共振频率依赖于缓冲气体密度和/或激发幅度的结果。共振的分辨率（从前体离子的消耗和碎片离子的形成来测量）随着K从1增加到6而提高了2倍。分辨率的这种提高值得进一步研究使用高阶共振来隔离和激发捕获离子。
