Chartkunchand K C, Stockett M H, Anderson E K, Eklund G, Kristiansson M K, Kamińska M, de Ruette N, Blom M, Björkhage M, Källberg A, Löfgren P, Reinhed P, Rosén S, Simonsson A, Zettergren H, Schmidt H T, Cederquist H
Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden.
Rev Sci Instrum. 2018 Mar;89(3):033112. doi: 10.1063/1.5010077.
A sputter ion source with a solid graphite target has been used to produce dianions with a focus on carbon cluster dianions, C, with n = 7-24. Singly and doubly charged anions from the source were accelerated together to kinetic energies of 10 keV per atomic unit of charge and injected into one of the cryogenic (13 K) ion-beam storage rings of the Double ElectroStatic Ion Ring Experiment facility at Stockholm University. Spontaneous decay of internally hot C dianions injected into the ring yielded C anions with kinetic energies of 20 keV, which were counted with a microchannel plate detector. Mass spectra produced by scanning the magnetic field of a 90° analyzing magnet on the ion injection line reflect the production of internally hot C - C dianions with lifetimes in the range of tens of microseconds to milliseconds. In spite of the high sensitivity of this method, no conclusive evidence of C was found while there was a clear C signal with the expected isotopic distribution. This is consistent with earlier experimental studies and with theoretical predictions. An upper limit is deduced for a C signal that is two orders-of-magnitude smaller than that for C. In addition, CO and CCu dianions were detected.
一种带有固体石墨靶的溅射离子源已被用于产生双负离子，重点是碳簇双负离子(C_n^{2 - })，其中(n = 7 - 24)。来自该源的单电荷和双电荷负离子一起被加速到每原子单位电荷(10 keV)的动能，并注入到斯德哥尔摩大学双静电离子环实验设施的一个低温（(13 K)）离子束储存环中。注入环中的内热(C_n^{2 - })双负离子的自发衰变产生了动能为(20 keV)的(C_n^ -)负离子，这些负离子用微通道板探测器进行计数。通过扫描离子注入线上(90°)分析磁铁的磁场产生的质谱反映了内热(C_n^{2 - })双负离子的产生，其寿命在几十微秒到毫秒范围内。尽管该方法具有高灵敏度，但未发现(C_n^{2 - })的确凿证据，而存在具有预期同位素分布的清晰的(C_n^ -)信号。这与早期的实验研究和理论预测一致。推导出(C_n^{2 - })信号的上限，其比(C_n^ -)信号小两个数量级。此外，还检测到了(CO^{2 - })和(CCu^{2 - })双负离子。
