Photoelectron Imaging And Theoretical Calculations Of Clusters Of Germanium

Ge_n^–(n=2-3)and Pb(OH)₂^–clusters have been studied using a laser vaporization time-of-flight mass spectrometer and a photoelectron velocity-map imaging instrument.The comparisons between these experiments and the theoretical calculations reveal their geometrical structures,electronic properties and bonding characters.The results help to understand the qualitative change from mico atoms or molecules to macro solid of elements of Ge_n^–(n=2-3)and Pb(OH)₂^–clusters and provide to theoretical guidance for important application in materials science field.The applications of germanium clusters in new technical fields are increasing rapidly,such as in infrared optics,superconducting materials,optical fibers and organic medicine,etc.Ge clusters are considered to be a very unique class of clusters,and their physical chemistry properties have attracted much attention.Anion photoelectron imaging spectroscopy combined with quantum chemical calculations have been used to deep look into the electronic properties of each structure of Ge_n^–(n=2-3)clusters,which including vertical detachment energy(VDEs),adiabatic detachment energy(ADE),geometries,electronic states,etc.Theoretical calculations were carried out at the?B97XD/6-311+G(3df)level to explore the ground states of the anionic and neutral Ge_n(n=2-3)clusters,and the molecular orbitals of Ge_n^–(n=2-3)were analyzed and discussed with the help of the natural bond orbital theory.The study found that transitions from Ge₂^–(²?_uD?h)to Ge₂(³?_gD?h),and the ADE and VDE are 2.03(7)and 2.12(7)e V,respectively.For Ge₃^–,the observed transition is from lowest-lying structure of Ge₃^–(²A₁ C_2v)to Ge₃(³A₂'D_3h),and the ADE and VDE is 2.23(6)and 2.30(6)e V,respectively.The anisotropy parameter(?)of ground state peaks are 0.92 for Ge₂^–,-1 for Ge₃^–.The Ge-Ge bond interaction is mainly reflected in the weak bonding between the 4P_x orbitals of the two germanium atomsIn addition,this paper also reported the anion photoelectron imaging spectroscopy study of Pb(OH)₂^–and Pb(OH)₂,and calculated the stable structure,ADE and VDE of neutral and anion clusters at the B3LYP/Pb/DZP/O,H/aug-cc-p VTZ level.The results shown that the structure of the ground state of the anion Pb(OH)₂^–is C₁ symmetric,with two hydroxyl groups attached to the same lead atom.The neutral Pb(OH)₂ cluster is enhanced by the symmetry due to the loss of an electron in an antibonding orbital by the corresponding anion,so that the ground state Pb(OH)₂ has the symmetry of C_s and C_2v.Molecular orbital analysis revealed that the vertical transition of Pb(OH)₂^–molecule was not obvious,and there was a weak antibonding property between lead and hydroxyl group.