Laser Spectroscopy For Uranium-Containing Diatomic Molecules And Construction Of Ion Velocity Imaging Apparatus

Actinide chemistry plays an important role in material science,nuclear waste disposal and nuclear fuel cycle.Due to the complexity of relativistic effect and electron correlation,the difficulty of experimental study of actinide chemistry and the lack of accurate theoretical calculation make the study of actinide molecules still have great challenges.In addition,the study of actinide chemistry is also very useful for the development of sensitive remote sensing spectroscopy of actinide molecules.Uranium is a typical important energy source in nuclear reaction and the most abundant actinide element on earth.It is widely used in various chemical forms of civil and military industries.Moreover,the 6p?6d?5f and 7s orbitals of uranium determine its atomic properties.Since these orbitals extend to bonding regions,these orbitals are greatly distorted by electrostatic effects and overlapping repulsion effects.The chemical properties of lanthanide are mainly determined by 4f orbitals,while the chemical properties of actinides are mainly determined by 5f orbitals.Therefore,it is of great significance to study heavy element compounds and nuclear waste cycles.Furthermore,these chemical bond properties can be well understood by studying small U-ligand gas phase molecules,especially when combined with theoretical models.Hence,in the case of nuclear energy,it is necessary to understand the molecules U-ligand bonding.Chemical reaction dynamics is a hot topic in chemical physics,and photolysis dynamics is an important branch of chemical reaction dynamics.Photolysis provides an important experimental method for understanding the dynamics mechanism of microscopic reaction.In the past half century,with the progress of laser technology,the study of photolysis dynamics has been developed rapidly.Now photolysis experiments have been extended to interstellar chemistry,environmental chemistry and combustion chemistry.In recent years,ion velocity imaging has become an important means to study photolysis dynamics.The main contents are as follows:1.The laser-induced fluorescence excitation spectra of UF have been recorded in the range of 17000-19000 cm^-1using two-dimensional spectroscopy.High resolution dispersed fluorescence spectra and fluorescence decay curves were also recorded.Three rotationally resolved bands have been intensively analyzed,and all bands were found to be derived from the ground state X(1)4.5 with a rotational constant of 0.23421 cm^-1.The low-lying electronic states have been observed near 435 and 651 cm^-1in the dispersed fluorescence spectra,which were assigned as?'=3.5,and 2.5,respectively.The vibrational constants for the X(1)4.5 and X(1)3.5 states have been calculated.The branching ratios of the dispersed fluorescence spectra for the[18.62]3.5,[17.72]4.5,and[17.65]4.5 states were reported.Radiative lifetimes of 332(9),825(49),and 433(15)ns for the[18.62]3.5,[17.72]4.5,and[17.65]4.5 states were obtained by fitting the fluorescence decay curves,respectively.Transition dipole moments were performed using the branching ratios and the radiative lifetimes.2.We use two-dimensional spectroscopy to investigated the laser-induced fluorescence spectra of UO in the range of 17500-18220 cm^-1.The UO of 11 rotationally resolved excitation bands were obtained.PGOPHER software simulation showed that these states come from the ground state X(1)4 or the first electronically excited state(2)4,and the ground state rotational constant of 0.33611 cm^-1was obtained.Six low-lying electronic states were found by the study of dispersed fluorescence spectra.The vibration constant of the X(1)4ground state was calculated to be 891 cm^-1.In this work,we also study the U¹⁸O isotopomers with two excited states were observed.And a ground state rotational constant B=0.29909cm^-1was obtained by fitting.3.Ion velocity imaging is a new technique developed in recent years to study photolysis kinetics.It can directly obtain the velocity three-dimensional distribution of the product,thus providing the most powerful tool for studying the orientation or orientation of the product.We have successfully built a set of ion velocity imaging apparatus with use of our new ion lens group.After the joint debugging of each system,we finally get the perfect effect and obtain the well-resolution image.4.Ion lens is the core of ion velocity imaging apparatus.Good design can make us get good experimental results.Based on this,we design a new type of ion lens and simulate it with simion software.The parameters of each electrode plate and the voltage of each electrode plate were optimized.