Steinbach C, Buck U
Max-Planck-Institut für Dynamik und Selbstorganisation, D-37073 Göttingen, Germany.
J Chem Phys. 2005 Apr 1;122(13):134301. doi: 10.1063/1.1863934.
In a continuous neat supersonic expansion ammonia clusters are generated and doped with sodium atoms in a pickup cell. Thus clusters of the form Na(NH(3))(n) are produced that are photoionized by a tunable dye laser system. The ions are mass analyzed in a reflectron time-of-flight mass spectrometer, and the wavelength dependent ion signals serve for the determination of the ionization potentials (IP) of the different clusters in the size range 10< or =n< or =1500. Aside from a plateau for 10< or =n< or =17 and smaller steps at n=24, 35, and 59 on the average a continuous decrease of the IP with cluster size is observed. The IPs in this size range are linear with (n+1)(-13) and extrapolate to IP(n=infinity)=1.66+/-0.01 eV. The slope is consistent with a dielectric continuum model of the solvated electron and the dielectric constant of the solid. The extrapolated IPs are compared with results obtained for negative ammonia cluster ions and metallic solutions in liquid ammonia. Differences are explained by the presence of counterions and their various distances from the solvated electron.
在连续纯净的超声速膨胀过程中，氨团簇在收集池中产生并掺杂钠原子。由此产生了Na(NH₃)ₙ形式的团簇，这些团簇被可调谐染料激光系统光电离。离子在反射式飞行时间质谱仪中进行质量分析，波长相关的离子信号用于确定尺寸范围为10≤n≤1500的不同团簇的电离势（IP）。除了10≤n≤17时的一个平台以及n = 24、35和59处的较小步长外，平均观察到IP随团簇尺寸持续下降。该尺寸范围内的IP与(n + 1)⁻¹³呈线性关系，外推至IP(n = ∞)=1.66±0.01 eV。斜率与溶剂化电子的介电连续体模型以及固体的介电常数一致。将外推得到的IP与负氨团簇离子和液氨中金属溶液的结果进行比较。差异由抗衡离子的存在及其与溶剂化电子的不同距离来解释。
