Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Universidad Nacional de La Plata, Casilla de Correo 16, Sucursal 4, La Plata 1900, Argentina.
Phys Chem Chem Phys. 2012 Mar 28;14(12):4276-86. doi: 10.1039/c2cp23510b. Epub 2012 Feb 21.
An experimental and theoretical study of the photoionization energies (IE's) of Ba(H(2)O)(n) clusters containing up to n = 4 water molecules has been performed. The clusters were generated by a pick-up source combining laser vaporization with pulsed supersonic expansion, and then photoionized by radiation of 272.5-340 nm. The experimentally determined IE(e)'s for n = 1 to 4 are 4.56 ± 0.05, 4.26 ± 0.05, 3.90 ± 0.05 and 3.71 ± 0.05 eV. This cluster size dependence of IE is reproduced within ±0.06 eV employing the mPW1PW91 density-functional and CCSD(T, Full) quantum-chemical methods combined with the 6-311++G(d,p) basis set for the H and O atoms and three different relativistic effective core potentials for Ba atoms. The calculations indicate that the lowest energy hydration structures represent the most relevant contributions to both the vertical and adiabatic ionization energies. Experimental and theoretical evidence correlates with the progressive surface-delocalization of the electron from the hydration cavity around the Ba atom and suggests that the intra-cluster electron transfer is possible even for small aggregates.
对含有多达 n = 4 个水分子的 Ba(H(2)O)(n) 团簇的光电离能 (IE) 进行了实验和理论研究。通过将激光蒸发与脉冲超音速膨胀相结合的拾取源生成了这些团簇，然后用 272.5-340nm 的辐射将其光致电离。实验确定的 n = 1 到 4 的 IE(e)' 值分别为 4.56 ± 0.05、4.26 ± 0.05、3.90 ± 0.05 和 3.71 ± 0.05eV。在 ±0.06eV 的范围内，使用 mPW1PW91 密度泛函和 CCSD(T，Full)量子化学方法结合 H 和 O 原子的 6-311++G(d,p)基组和三种不同的 Ba 原子相对论有效核势，重现了这种 IE 的团簇尺寸依赖性。计算表明，最低能量水合结构对垂直和绝热电离能都有最重要的贡献。实验和理论证据与电子从 Ba 原子周围水合腔的表面离域化的逐步进行相关联，并表明即使对于小的聚集体，也可能发生 intra-cluster 电子转移。
