Spectroscopic study of novel cluster structures created as chemical intermediates in supersonic molecular beams

对喷射冷却的分子团簇阳离子进行了光谱研究，研究了以下体系：1。[C_6H_6（NH_3）_n]^+（n=1和2）的红外光谱和电子光谱表明，它们的稳定形式为S-络合物型，其中氨部分与苯部分共价键合，是芳烃亲核取代反应的中间体。结合量子化学计算，研究了[苯-（甲醇）_n]^+（n=2，3）的类似结构.用红外光谱研究了H^+（H_2O）_n（n=20-200）的氢键网络结构。结果表明，随着团簇尺寸的增大，团簇的光谱特征逐渐变得与水和冰的特征相似，表明大尺寸团簇的网络形态逐渐向块状团簇的网络形态转变。利用真空紫外单光子电离红外光谱研究了丙酮和乙酸的中性和阳离子团簇的结构。结果表明，许多团簇，如它们的二聚体，在电离后产生酮-烯醇跃迁，而它们的中性体是酮-形式。从质子亲合势和质子转移坐标的势能面讨论了异构化机理。

Spectroscopic studies on jet-cooled molecular cluster cations have been carried out for the following systems ;1. IR and electronic spectroscopy of [C_6H_6(NH_3)_n]^+ (n=1 and 2) revealed that their stable forms are of s-complex type, in which the ammonia moiety is covalently bonded to the benzene moiety as expected as the reaction intermediate of nucleophilic substitution of aromatics. The similar structures of [Benzene-(Methanol)_n]^+ (n=2, 3) were also investigated in combination with quantum chemical calculations.2. H-bond network structures of H^+(H_2O)_n (n=20-200) were investigated by IR spectroscopy. It was found that the spectral features of the clusters with increasing cluster size become similar to the characteristic features of water and of ice, indicating the network morphology of the large-size clusters transmutes gradually to those of the bulk systems. It was also found that the spectral feature depends on the internal energy in the species.3.Structures of neutral and cationic clusters of acetone and of acetic acid were investigated by using IR spectroscopy based on vacuum-ultraviolet one-photon ionization detection. It was found that the keto-enol transition is generated after the ionization for many clusters, such as their dimers, whereas their neutrals are of the keto-form. The isomerization mechanism was discussed in relation to their proton affinities and the potential surface of the proton-transfer coordinate.