Raston Paul L, Jäger Wolfgang
Department of Chemistry and Biochemistry, James Madison University , Harrisonburg, Virginia 22807, United States.
Department of Chemistry, University of Alberta , Edmonton, Alberta T6G 2G2, Canada.
J Phys Chem A. 2017 May 18;121(19):3671-3678. doi: 10.1021/acs.jpca.7b02192. Epub 2017 May 9.
We report the Fourier transform microwave spectra of (pH)-CO, (pH)-CO, and (pH)-CO (N ≤ 8) clusters. We find that the frequencies of the a-type J = 1-0 transitions decrease to a minimum at N = 6 and then rapidly increase up to at least N = 8; this is similar to what was previously reported for (pH)-CO, for which the turnaround was found to correlate with an increase in the superfluid fraction of the pH component of the clusters [ Raston Phys. Rev. Lett. 2012 , 108 , 253402 ]. The data suggest that the turnaround in the transition frequency marks an abrupt decrease in the anisotropy of the potential (i.e., in going from N = 6 → 7 → 8), as evidenced from the isotopologic differences rapidly evolving from end-over-end to free-rotor character. Structurally, a more quantitative analysis of the anisotropy was hindered by the lack of accurate frequencies in the b-type series, and a simple Kraitchman analysis yielded unphysical results. In addition to comparing the transition frequencies of the different isotopologic clusters, we provide here more comprehensive details and further discussion of the initial measurements made on (pH)-CO.
我们报道了（pH）-CO、（pH）-CO和（pH）-CO（N≤8）团簇的傅里叶变换微波光谱。我们发现，a型J = 1-0跃迁的频率在N = 6时降至最低，然后迅速增加至至少N = 8；这与之前报道的（pH）-CO情况类似，之前发现其转折与团簇pH组分的超流分数增加相关[Raston《物理评论快报》2012年，108卷，253402页]。数据表明，跃迁频率的转折标志着势的各向异性突然降低（即从N = 6到7再到8），这从同位素拓扑差异从端对端迅速演变为自由转子特征可以看出。在结构上，b型系列中缺乏准确频率阻碍了对各向异性进行更定量的分析，简单的克莱奇曼分析得出了不符合实际的结果。除了比较不同同位素拓扑团簇的跃迁频率外，我们在此还提供了关于（pH）-CO初始测量的更全面细节和进一步讨论。
