Mass spectra of doped and undoped helium droplets are presented. The high resolution of the time-of-flight spectrometer (m/Δm ? 5000) makes it possible to fully resolve small helium cluster ions from impurities and to unambiguously identify abundance anomalies in the size distribution of He_ n~+. The yield of He_4~+ shows the well-known enhancement relative to other small cluster ions when the expansion changes from sub- to supercritical, provided the electron energy exceeds a value of 40 ± 1 eV, the threshold for formation of electronically excited ions. Upon doping with krypton, pure Kr _n~+ cluster ions containing up to 41 Kr atoms are observed. The spectra exhibit abundance anomalies at 13, 16, 19, 22 & 23, 26 and 29, in agreement with spectra obtained by ionization of bare krypton clusters that are formed in neat supersonic beams. Mixed clusters He m Kr~+ indicate closure of a solvation shell at m = 12.
展开▼
机译：给出了掺杂和未掺杂氦气滴的质谱图。飞行时间光谱仪的高分辨率（m /Δm≤5000）使得可以完全分辨来自杂质的小氦团簇离子，并可以明确识别He_n〜+尺寸分布中的丰度异常。当电子膨胀超过40±1 eV（形成电子激发离子的阈值）时，当膨胀从亚临界变为超临界时，He_4〜+的产率显示出相对于其他小簇离子的众所周知的增强。掺杂k后，观察到纯的Kr _n〜+簇离子包含多达41个Kr原子。光谱在13、16、19、22和23、26和29处显示出丰度异常，这与通过在纯超声束中形成的裸k簇的电离获得的光谱一致。混合簇He m Kr〜+表示在m = 12时溶剂化壳的封闭。
展开▼
