^(12)C^(16)O精确的半经验势能面、振转光谱及温度压强效应研究

Accurate Semi-Empirical Potential Energy Function,Ro-Vibrational Spectrum and the Effect of Temperature and Pressure for ^(12)C^(16)O

伴随高超音速飞行器、无接触诊断等技术的快速发展,更多分子谱带被激发,对高温高压下的振转光谱数据需求急剧增加,加之高灵敏、高分辨激光光腔衰荡(CRDS)、可调谐半导体激光吸收(TDLAS)等光谱技术的快速进步,相应分子的振转光谱研究被进一步推进。CO作为高温燃烧的重要产物,对其研究首当其冲。首先利用实验决定的(ν<41)^(12)C ^(16)O基态Dunham参数,通过Rydberg-Klein-Rees(RKR)方法,反演出分子平衡核间距附近的局域离散势能点;接着将其拟合到十多个常见的解析势能函数(PEF),发现SPF和Morse函数具有较好的拟合精度,但在长程上依然不符合物理要求;在此基础上结合实验获得的解离能对长程进行校正,构建了一个全新的、半经验、全局、解析势函数Revised-Morse,并通过多参考组态相互作用理论(MRCI)确认了其合理性,该函数既能精确再现低振动态能级,也能合理预测未知高振动态能级,且具有精确的解离极限。接着通过multireference averaged coupled-pair functional(ACPF)理论方法结合差分技术,得到了三种电场下^(12)C ^(16)O基态(ν<63)的偶极矩面(DMs)。基于构建的Revised-Morse势函数和DMs,通过求解一维薛定谔方程得到了直到解离极限的振转能级,计算结果与文献值十分吻合,表明Revised-Morse函数是十分可靠的。基于此得到了常温下所有的跃迁谱线位置,ν<63时的爱因斯坦系数、谱线强度等光谱数据,计算值与HITRAN数据库中的结果几乎完全一致,同时振动跃迁偶极矩、辐射寿命、离心畸变等光谱常数也被一并获取。该研究不仅完美再现了已知谱带,还预期了几十万条新的跃迁谱线,一些新的光谱参数也被报道,可为光谱探测提供参考。为建立基于^(12)C ^(16)O的测温模型,继续考察了温度直到9000 K的配分函数,模拟了不同温度下的振转光谱,以20000 cm^(-1)(对数坐标)以下和ν0-1带(线性坐标)的线状谱图为示例说明了谱线随温度的变化情况,并提出了几种可能的测温方案线索。最后考察了压强对振转谱线的影响。

With the rapid development of high-supersonic aircraft,non-contact diagnosis technology,etc,more molecular bands are excited,and the demand for rovibrational spectrum data under high temperature and high pressure has increased dramatically.In addition,with the rapid improvement of the cavity ring-down spectroscopy(CRDS),and the tunable semiconductor laser absorption spectrum technology(TDLAS)with high sensitivity,the research on the corresponding spectrum are promoted further accordingly.CO,an important product of high-temperature combustion,is the first to be investigated.In this paper,firstly,the local discrete potential energy points near the molecular equilibrium internuclear separation were obtained employing the Rydberg-Klein-Rees(RKR)method,with the use of spectral parameters of the ^(12)C ^(16)O on the ground state(vibrational quantum numberν<41)determined by the experimental.Then it is fitted to more than ten common analytical potential functions,and it is shown that the SPF and Morse functions have good fitting accuracy,but they are still unreasonable on the long-range part.Because of this,the dissociation energy from the experiment is adopted for revising the long-range part,and a new,semi-empirical,global potential function named Revised-Morse was constructed,which not only could accurately reproduce the known vibrational levels but reasonably predict the unknown high vibrational levels with accurate dissociation limit.The multi-reference configuration interaction method(MRCI)was used confirmed its rationality.The levels with highνcalculated in this paper agree with the result from the literature.Secondly,the electronic dipole moment surfaces(DMs)of ^(12)C ^(16)O on the ground state at vibrational quantum numberν<63 under three kinds of electric fields were obtained using the multi-reference averaged coupled-pair functional(ACPF)theory combined with differential technology.Based on the above Revised-Morse potential function and DMs,the vibrational and transition levels up to the dissociation limit,and the transition moment,line strength,Einstein coefficient and intensity at room temperature withν<63 were obtained by solving the one-dimensional Schrodinger equation,meanwhile,the spectral constants such as radiation lifetime and centrifugal distortion were also obtained.The calculated values are almost completely consistent with the results from the HITRAN.This paper not only reproduces the known spectral bands perfectly but also predicts hundreds of thousands of new spectral lines and some new spectral parameters,which can provide a reference for spectral detection.To establish the temperature measurement model based on ^(12)C ^(16)O,the partition function of temperature below 9000 K was further investigated,and the rovibrational spectra at different temperatures were simulated.The variation of the spectral line with temperature was illustrated by the line spectrogram below 20000 cm^(-1)(logarithmic coordinate)andν0-1 band(linear coordinate).Several possible temperature measurement model schemes are proposed.Finally,the influence of pressure on the rovibrational line is discussed.