团簇尺寸对奇数和偶数磷团簇离子信号强度差异的影响

磷原子形成的奇数和偶数团簇离子的信号存在明显的强度差异. 当团簇离子尺寸n>25时, 奇数团簇离子的信号强度一般会远远超过其邻近的偶数团簇离子. 为更好地理解团簇尺寸对这一现象的影响, 本文通过真空中激光溅射红磷的方法, 利用质谱对磷团簇离子进行了研究和分析. 结果表明这种方法可以产生较大尺寸(n~500)的磷团簇离子. 进一步对团簇离子的强度分布进行分析表明: 随着正负离子团簇尺寸的增加, 奇/偶数离子强度差异都会逐渐减小. 根据它们的变化趋势, 可以预测: 当n>1000时, 奇/偶数离子强度交替的现象可能会消失. 这一结果正反映出团簇在从原子演变到凝聚态物质过程中的桥梁作用.

Size Effect on the Signal Intensity Difference between Odd-and Even-Numbered Phosphorus Cluster Ions

Intensity difference between odd- and even-numbered cluster ions is one of the characteristics of phosphorus clusters. Generally, for the clusters with cluster ion size n>25, intensities of odd-numbered cluster ions are much higher than those of their even-numbered neighbors. In order to better understand the size effect on the phenomenon, large phosphorus clusters (n~500) were generated by laser ablation on red phosphorus in vacuum. Their intensity distributions were also analyzed. Results show that the intensity difference between odd- and even-numbered cluster ions decreases with increasing cluster size for both cations and anions. Based on the observed trends for cations and anions, it can be estimated that the observed intensity alternation of even/odd numbered clusters may vanish for cluster ions with n>1000. These results exactly reflect the function of cluster as a bridge linking atoms in the gas phase and their bulk counterpart in the bulk phase.