Radiative Association And Rovibrational Spectra Of CO

Gas thermal radiation plays an important fundamental role in energy transfer and signal transmission.Accurate data of radiative association and rovibrational spectra for diatomic molecules are critical for thermal design of hypersonic vehicles,ablation process detection,combustion process control,target identification and diagnosis,monitoring and evaluation of the earth’s atmospheric environment,formation and evolution of celestial bodies,plasma transport simulation,etc.However,early studies on gas radiation only involved discrete spectra at low temperatures.At high temperatures,gas molecules are generally in a high-energy electronic state,which is prone to physical and chemical processes such as radiative association,and then radiates stronger spectral lines than at low temperatures,which significantly affects the calculation of the high-temperature gas radiation field.Therefore,taking the extremely important CO in the earth’s atmosphere and the interstellar medium as an example,this thesis explains the research method for the radiative properties of CO,and calculates the important electronic structure data,radiative association cross sections and rate coefficients,and the rovibrational spectra for CO.Electronic structure data is the basis for studying the radiative association and rovibrational spectra.Considering scalar relativistic effect,valence electron correlation effect and core-valence correlation correction,the potential energy curves of the 22 electronic states for CO and the associated dipole moment were calculated using the internal contraction multireference configuration interaction method and the aug-cc-pwCV5Z-DK basis set.The spectroscopic constants of 18 electronic states were obtained by solving the bound and quasibound energy levels of the radial Schrodinger equation.The calculated spectroscopic constants are consistent with the experimental and theoretical results in the papers.Taking the A 1∏ state as an example,the radiative lifetime was calculated.In addition,the static dipole polarizabilities of C(2s22p2 3P,2s22p2 1D)and O(2s22p4 3P,2s22p4 1D)were calculated.Molecules undergo the radiative association process and emit continuous spectra.The cross sections of the radiative association of C(2s22p2 3P)and O(2s2p4 3P)for collision energies in the range of 0.00001-10 eV were calculated using the quantum-mechanical approach,which extended the continuous spectra data of CO.Based on the Maxwell-Boltzmann distribution of particles under equilibrium conditions,the rate coefficients of CO in the temperature range of 10-10000 K were obtained,which can provide fundamental data for the molecular reaction dynamics.The results show that CO is mainly formed through the radiative association processes A 1∏-X1∑+,B 1∑+-X 1∑+,a’ 3∑+-a 3∏,d 3Δ-a 3∏ and e 3∑--a 3∏.The total rate coefficient of the radiative association for CO is of the order of 1.18 × 10-18 to 1.31 ×10-16 cm3 s-1 for temperatures of 10-10000 K.Establishing a complete model of the rovibrational spectra for CO is essential for photothermal radiation research.The relation between the measurable transitions and the theoretical energy levels in spectroscopy is linear and exceedingly simple,therefore 1373 empirical energy levels with reliable uncertainties were obtained from 9692 transitions of 5 electronic bands,which can correct the calculated electronic structure data.Based on the corrected data,the rovibrational spectra at 300 K,3000 K and 8000 K temperature of CO was calculated,considering the eight lowest electronic states:X 1∑+,a 3∏,a’ 3∑+,d 3A,e 3∑+,A 1∏,I 1∑-and D 1Δ.In order to verify the accuracy of the obtained spectra,the resonant electron absorption spectra of CO at room temperature was simulated,which was in good agreement with the experimental spectra.