The Laser Spectroscopic And Mass Spectrometric Investigations Of The Gas Phase Tungsten Compounds

The transition-metal compounds,e.g.the tungsten containing compounds,have many high electron spins,strong spin-orbit coupling and complicated electronic state structure,which resulting the spectroscopic studies are very limited.The main work of this thesis is to study the tungsten compounds,i.e.WO,WS,[W?CO?₆]⁺and[Re?CO?₆]⁺molecules,by laser spectroscopy and mass spectrometry.On the one hand,the spectroscopic constants of these molecules obtained through analysis of the rovibrational-resolved spectra help to understand the chemical bonding and internal molecular interaction.On the other hand,the chemical reaction kinetic characteristic of these transition metal atoms is investigated through the high-precision mass spectrometry experiments that provides a direct data reference for the study of chemical property of the homolog superheavy elements.First of all,we designed and built the laser spectroscopy and mass spectrometry experimental platform,and tested the production of the radicals,the properties of the molecular beam and the quality of the mass spectrometry.The results showed that the gas discharge plasma can effectively dissociate a large number of metal clusters which are created by laser ablation on metal target into smaller fragments and react with gas plasma to produce free radicals of target metal compounds.After supersonic jet cooling,these compounds have very low vibrational and rotational temperature,which is proved to be suitable for laser spectroscopic experiment.In addition,a Wiley-McLaren time-of-flight?TOF?mass spectrometer is optimized that the mass resolution?m/?m?is better than 1500,which provides a guarantee for the subsequent heavy ionic compound experiments.Secondly,the low-energy electronic structure of WO radical was studied by high-resolution laser spectroscopy.By using the discharge assisted laser ablation source combined with the O2/Ar mixture,we have prepared the gas-phase WO radicals,and systematically studied the laser-induced fluorescence?LIF?spectrum in the range of 18900-23500 cm^-1.Four new electronic transition systems[21.2]0⁺–X0⁺,[22.2]0⁺–X0⁺,[21.5]0⁺–X0⁺and[23.3]1–X0⁺have been observed.Through the fitting of the rovibrational resolved spectra,the accurate molecular constants in electronic excited states are derived,including vibrational frequency,anharmonic term,electronic origin,rotational constant,centrifugal distortion and lifetime etc.In addition,we observe the abnormal isotope shifts in the two newly observed transition bands,which are explained by the interaction between interbands.Combining with the results of previous emission spectrum experiments,it can be confirmed that all the electronic states with?<3 in the experimental energy range are observed.And five0⁺symmetry electronic states observed in the experiment are more than the two 0⁺symmetry states that predicted by the theoretical calculation,which need higher precision theoretical calculation to verify in order to understand the complex electronic structure of WO molecule.Thirdly,the low-lying electronic structure of WS radicals was studied experimentally.The WS radicals were prepared by laser ablation of tungsten disulfide?WS₂?target.The LIF spectra in the range of 13100-21500 cm^-1 were investigated.Totally 42 vibrational bands have been observed,which belong to 11 electronic transitions.According to the analysis of the rovibrational spectra,the spin-orbit splitting interval of WS molecular in ground state is accurately determined as2181.10?9?cm^-1.The accurate molecular constants in electronic excited states are obtained,including electronic origin,vibrational frequency,anharmonic term,rotational constant?bond length?,centrifugal distortion,excited state lifetime,etc.In addition,the spin-orbit components of the first and the second excited electronic states,as well as the complete information of the energy levels of the 6th to 12th electronic states with?=1,are distinguished in the experimental results,which provide the benchmarch database for high-precision quantum chemistry calculation on the electronic structure of the transition metal compounds that have strong electron-electron correlation and strong spin-orbit coupling interaction.Finally,the TOF mass spectrometry of the molecular reaction kinetics of W/Re carbonyl compounds were studied.We investigate the stable reaction products under the condition of excess CO reacting with the atomic and ionic products produced by laser ablation of pure metal Re and W targets under different proportions of He and impurity gases?O₂,H₂ and H₂O?.At the same time,we have performed the high-precision DFT calculation,and found that the stable products of W/Re ion and excess CO reaction are[Re?CO?₆]⁺and[W?CO?₆]⁺ions,which are consistent with the experimental results of TOF mass spectrometry,and provide direct data reference for the next step experiment on Bh element monoatomic carbonyl chemical reaction.