Photoelectron Spectroscopy Studies Of Anion Clusters

Clusters are a class of stable?submicroscopic?aggregates consisting of several or even hundreds of atoms and molecules,that widely exist in a natural system of solids,liquids,and gases and represent a new state of matter between isolated molecule and bulk material.In the cluster science,anion cluster is an important object,which has a wide range of applications in atmospheric environment,new energy technology,targeted drug synthesis and industrial production.With the development of ultra-high resolution photoelectron spectroscopy,the ultrafast dynamics of the photochemical reaction of anion clusters can be studied in molecular level.Combined with high-level quantum chemistry calculation,the measured momentum and kinetic energy of photoelectron can reveal the electronic structure,intermolecular interaction,and quantum size effect of anion cluster.Thus,further investigation of the interaction between anion cluster and laser field is not only the frontier exploration of electronic ultrafast dynamics in complex systems,but also provides experimental and theoretical support for the extensive application of cluster in related areas.In this thesis,based on the negative ion photoelectron spectroscopy,we have investigated the electron binding energies,electronic structures,and noncovalent interactions of the anion clusters,such as NaS_n^-?n=5-9?,?-CD·B₁₂X₁₂^2-??=?,?,?;X=H,F?,and[?H₃N·SO₃?_n-H]^–?n=1,2?,which have potential application in energy,medicine,atmospheric environment.This thesis mainly includes the following contents:1.Based on the negative ion photoelectron spectroscopy,the electron binding energies of NaS_n^-?n=5-9?are measured,and we have indirectly characterized the intrinsically electronic structures of the S_n^2-with fleeting lifetimes in the gas phase.The experimental results indicate that NaS_n^-are essentially contact ion pairs,in which Na⁺and S_n^2-electrostatically interact with each other.The photoelectrons are mainly derived from S_n^2-.The electronic stabilities of NaS_n^-clusters increase with the number of S atoms.2.The electronic structures and noncovalent interactions of?-CD·B₁₂X₁₂^2-complexes are studied.The experimental results show that the binding interactions between?-CD and B₁₂X₁₂^2-result in the inclusion complexes,and the size matching effect and molecular specificity have a significant influence on the electron binding energy,noncovalent interaction and the inclusion extent.The inclusion of B₁₂X₁₂^2-into?-CD cavities greatly increases the electronic stabilities of the dianions.Theoretical calculation indicates that the competitive mechanism has been observed in the noncovalent interaction of?-CD·B₁₂X₁₂^2-,which is dominated by electrostatic interaction.The special dihydrogen bonds are observed in?-CD·B₁₂H₁₂^2-,and the influence of strong dihydrogen bonds on the interaction between?-CD and B₁₂H₁₂^2-has been revealed.3.The electron binding energies and noncovalent interactions between sulfamic acid monomer and dimer are investigated.The experimental results show that the electronic stability is significantly enhanced by the multiple H-bonds in dimer.The dimer consists of two binding modes,one corresponding to the zwitterion configuration and the other corresponding to the neutral configuration of neutral sulfamic acid.The former consists of three N-H…O bonds,while the latter is composed of two N-H…O bonds and one O-H…O bond.Theoretical results show that H-bonds are dominated by electrostatic interaction in the dimer.The strong binding energy of O-H…O bond can be attributed to its high polarization.These studies give a molecular-level understanding for the primary homogeneous nucleation of sulfamic acid clusters.