Electronic Structure And Relativistic Effect Of The Transition Metal Monoxides And Monosulfides

The electronic structure of transition metal molecules has fundamental importance for examining basic physical problems such as quantum electrodynamics（QED）and fundamental symmetries of physical laws,optimizing the computational method and program in modern quantum chemistry,probing stellar compositions and evolution,and predicting the chemical properties of superheavy-elements.However,the molecule containing a heavy-element transition metal atom has complex electronic structure and optical spectra,due to the significant electron correlation and relativistic effect.Up to now,high-precision spectral experiment and theoretical calculation data for many heavy element transition metal molecules,especially the simplest diatomic molecules,are still very limited,and even many molecules have not been reported.In this work,laser ablation and supersonic jet cooling techniques were used to successfully generate the Cr O,Cr S,Mo O,WO,and Pd S.The high-resolution excitation spectra and emission spectra of these molecules were observed using laser-induced fluorescence（LIF）spectroscopy,By the spectral analysis,the accurate molecular constants and the information of the electronic structure were obtained.Based on the properties of the ground electronic states of the molecules,the relativistic effects in the group 6 and group 10 transition metal transition metal monoxides（monosulfides）were revealed and extended to understand the relativistic effects in the 5d transition metal monoxides（monosulfides）.The main research contents and results are as follows:（1）The excitation spectra and emission spectra of the Cr O and Cr S molecules were observed in the energy ranges of 13800–23200 cm^-1 and 14950–16450 cm^-1,respectively.The ground state X ⁵Πand the excited state B ⁵Πwere studied.For Cr O,the rotational constants of X ⁵Π_-1（v′′=0–3）,B ⁵Π_-1（v′=0–10）,and B ⁵Π₁（v′=1,5）,the vibrational constants of X ⁵Π_-1,0,1,and the lifetime of B ⁵Π_-1（v′=0–10）were obtained.For Cr S,the rotational constants of B ⁵Π_-1（v′=7）,the vibrational constants of X ⁵Π_-1,and the lifetime of B ⁵Π_-1（v′=0–7）were obtained.（2）The excitation spectra and emission spectra of the Mo O molecule were observed in the energy range of 13800–23580 cm^-1,and the low-lying electronic structure and the isotope shifts in the optical spectra were studied.The spin-orbit components of X ⁵Π,a ³Σˉ,and b ³Δwere fully observed,as well as the spin-orbit splittings and rovibrational constants.In addition,four excitation bands with significant isotopic-resolution characteristics were found,and the rovibrational constants of^{92,94,95,96,97,98,100}Mo O were obtained.In addition,the influence of the isotopic effects on the energy level was analyzed.（3）The vibrationally resolved emission spectra of the WO molecule were observed,and the spin-orbit splitting of the ground electronic state was studied.The emission spectra were assigned with the help of Franck-Condon factors calculation and proved that the two excited states D′1 and[23.3]1 are a common state.Therefore,the separation between the two spin componentsΩ′′=0⁺and 1 of the ground state X ³Σˉwas determined.In addition,some previously observed electronic states were reassigned,and a new energy level diagram of WO was constructed.（4）The high-resolution laser spectra of the Pd S molecule was observed for the first time.The electronic structure was studied by the analysis of the rotationally and isotopically resolved excitation spectra of I ³Σˉ-X ³Σˉand the vibrationally resolved emission spectra of I ³Σˉ–A ³Π&X ³Σˉ.The molecular constants of ^{104,105,106,108,110}Pd O were obtained.By comparing the results of ab initio calculations,a comprehensive understanding of the electronic structure of Pd S has been achieved,especially an accurate understanding of the characteristics of the ground and low-lying electronic states.With the inclusion of this work,the absence of the optical spectra of Pd S in the group 10 transition metal monosulfides has been filled.（5）Based on the above results and literature data,the properties（including electron configuration,spin-orbital splitting,bond length and vibration frequency）of the ground electronic state of all transition metal monoxides（monosulfides）were summarized,and the change rules of the properties of the ground state of the same group compounds were compared and explained.As a result,the contribution of the relativistic effect to the bonding of the 5d transition metal monoxides（monosulfides）were revealed.In this paper,the laser spectra of Cr O,Cr S,Mo O,WO,and Pd S molecules have been accurately measured,and the effects of perturbation and isotope displacement in the molecules have been analyzed.High precision molecular constants have been obtained,revealing the role and laws of the relativistic effects in the oxidation of heavy element atoms into bonding.It provides reliable test data for improving the theoretical model of high-precision quantum chemical calculations and predicting the electronic structure and chemical properties of the heavy element compounds.