Investigation Of The Electronic Structures And Chemical Bonding Of Beryllium-Contained Molecules And Clusters

The research of electronic structure and angular distribution of beryllium-contained molecules and clusters have been carried out using laser evaporation cluster source,time-of-flight mass spectrometer and photoelectron velocity map imaging technology.The bonding analysis for this beryllium-contained species can improve the understanding of beryllium chemical bonding,which is useful to explain the toxicity of beryllium compounds and the excellent physical properties of beryllium-contained materials.Herein,electronic structure and angular distribution of several of beryllium-contained molecules and clusters(（BeO₂^-,Be₂O₂^-,Be₂O₃^-,Be₂F₃^-,FBeO^-,FBe S^-）have been measured based on photoelectron imaging,then combined with quantitative calculation to analyze how beryllium to participate bonding.The main results are as follows:（1）The photoelectron imaging apparatus has been improved in many aspects.Firstly,the utilization rate of the sample was improved by adding a flat rotating design on the ion source.Then cold beryllium-contained molecules and clusters were produced by using various ion source structures.Finally,the photoelectron velocity map imaging lens system was improved with resolution from 4%to 1.6%.（2）Two Be₂O₂^-isomers that rhombic structure and linear structure have been observed in photoelectron spectra.The EA of rhombic Be₂O₂ is 1.016 e V.The bond analysis indicate there is a special“hollow Be–Be bond”.The bond results in a frequency change of 411 cm^-1 of vibronic modeυ₄.The EA of linear BeOBeO is 2.880 e V.Bond analysis indicates that electrostatic interaction between Be and O is the main forces,but p orbital electron of O atom entering the vacant p orbital of Be atom play an important role.The electron detachment result in a big change of bonding strength.（3）The photoelectron spectra of BeO₂^-and Be₂O₃^-show that the EA of BeO₂ is 3.476 e V and the EA of Be₂O₃ is 2.991 e V.The electronic structure of BeO₂ andBe₂O₃ is very complex due to the influence of muti-configuration effect so that the density functional method（DFT）without considering the electron correlation can’t give coincident experimental result.The chemical bond analysis shows that the Be–O bonding includes the Be–Oσbond,dativeπbond that the p orbital electron of O atom entering the vacant p orbital of Be atom and the electrostatic interaction.（4）Two Be₂F₃^-isomers have been observed in the photoelectron spectra.The isomer FBe–BeF₂ with Be–Be bond is global minimum.Bond analysis indicates that there is a special“Be–Be dative bond”with a bond energy of 44 kcal/mol.The isomer BeF–BeF₂ with Be–F bond have an EA of 2.241 e V.Bond analysis indicates that the Be–F bond depends on electrostatic interaction,the anion and neutral molecule show different bond energy of 34.4 kcal/mol for anion and 15.9 kcal/mol for neutral molecule.（5）The photoelectron spectra of FBeO^-and FBe S^-show that the EA of FBeO is 3.038 e V and the EA of FBe S is 3.085 e V.The spin orbital splitting characteristics can be observed in photoelectron spectra of FBe S^-with a splittingenergy of 347 cm^-1.Both molecules are linear structure.Bond analysis suggest that Be atom ³P excited state and Be²⁺ionic state both have significance for bonding.Be–O bond is stronger than Be–S bond due to stronger electrostatic interaction between Be atom and O atom.