Study of electronic states and geometry of size-selected clusters by means of an electron-ion multiple coincidence spectroscopy

为了高效地产生稀有气体团簇，研制了一套团簇产生系统。将该系统安装在电子-离子多重符合装置上，研究了尺寸选择团簇的去激发机制，观察到Ar二聚体从俄歇末态到双阳离子态的原子间库仑衰变（ICD）。通过光电离产生的2 p内壳层空位通过原子内俄歇衰变被3s和3 p空位取代。俄歇末位双阳离子态是一个ICD过程，在这个过程中，同一Ar原子中的一个3 p电子填充3s空位，而相邻Ar原子中的一个3 p电子作为ICD电子被发射出去，通过电子-离子-离子符合谱，ICD电子的动能以及Ar^+和Ar^&lt;2+&gt;之间的动能释放，可以清楚地确定这个ICD过程与Ar ^2 ^&lt;2+&gt;产生的两个Ar^+离子同时记录的俄歇电子能谱表明，束缚的单格位双空穴态Ar^&lt;2+&gt;（3 p ^<-2>）-Ar进一步衰变只能通过辐射电荷转移到离解的双格位双空穴态Ar^+（3 p ^<-1>）-Ar^+（3 p ^<-1>）。

A cluster generation system was made in order to produce rare gas clusters efficiently. This system was mounted on an electron-ion multiple coincidence apparatus and de-excitation mechanism of size-selected clusters was investigated.Interatomic Coulombic decay (ICD) from an Auger-final dicationic state is observed in the Ar dimer. A 2p inner-shell vacancy created by photoionization is replaced with 3s and 3p vacancies via intra-atomic Auger decay. The Auger-final dicationic state is subject to ICD in which one of the 3p electrons in the same Ar atom fills the 3s vacancy while one of the 3p electrons from the neighboring Ar atom is emitted as an ICD electron. This ICD process is unambiguously identified by electron-ion-ion coincidence spectroscopy in which the kinetic energy of the ICD electron and the kinetic energy release between Ar^+ and Ar^<2+> are measured in coincidence.Auger electron spectra recorded in coincidence with two Ar^+ ions produced from Ar_2^<2+> suggest that the bound one-site two-hole state, Ar^<2+>(3p^<-2>)-Ar, decays further only via radiative charge transfer to the dissociative two-site two-hole states Ar^+(3P^<-1>)-Ar^+(3p^<-1>) The measured kinetic energy release of Ar_2^<2+> agrees well with the theoretical estimate based on this process.