基于SO分子振转能级计算其宏观气体摩尔热容

Calculating macroscopic gas molar heat capacity of SO molecule based on rovibrational energy level

本文在研究SO宏观气体摩尔热容的工作中,进一步考虑了分子内部的转动贡献,通过联立能获得分子某电子态完全振动能级的变分代数法(variational algebraic method,VAM)和RKR(Rydberg-Klein-Rees)方法构建了SO电子基态的势能函数,解析求解获得了该体系的振转能级,进而采用量子统计系综理论计算得到了300-6000 K温度范围内SO宏观气体的摩尔热容.将本文的计算结果与其他几种理论模型的计算结果进行比较分析,结果表明:当采用基于全程势能曲线求解的完全振转能级来计算热力学性质时,得到的摩尔热容与实验结果更为吻合.本文利用分子完全振转能级计算摩尔热容的思路,弥补了前一阶段工作中仅采用近似模型表征分子转动行为来计算热容的不足,为基于微观统计过程求解宏观热力学量提供了新的研究范式.

Sulfur oxide(SO)is a kind of well-known diatomic molecule which becomes one of the major pollutants in the atmosphere.Control of the heat capacity of SO molecule is of great significance for elucidating its macroscopic evolution process.In the research of macroscopic systems composed of many particles as well as several matters,it is an important approach to obtain macroscopic thermodynamic quantities of the system by constructing a partition function from the microscopic information of molecule.For diatomic molecules in a certain electronic state,the partition function can directly be obtained by calculating the rovibrational energy of the system to acquire the macroscopic molar heat capacities.In this work,the contribution of rotational behavior to molar heat capacity is further considered.The potential energy function for the ground electronic state of SO is constructed by the variational algebraic method(VAM)and RKR(Rydberg-Klein-Rees)method,in which the former one can determine the complete vibrational energy levels of an electronic state of a molecule.The rovibrational energy level of the system is obtained by analytical solution,and then the molar heat capacity of SO macroscopic gas in the temperature range of 300-6000 K is calculated by quantum statistical ensemble theory The above calculation depends only on the experimental vibrational energy,experimental rotational spectral constant and the dissociation energy of SO molecule.Fortunately,through comparison between theoretical calculation results and experimental data,we find that the molar heat capacity of gaseous SO molecule can be well predicted by employing the full set of rovibrational energy to describe the internal vibration and rotation of SO molecule.The idea of calculating the molar heat capacity by using the full set of rovibrational energy makes up for the shortcomings of previous work where molar heat capacity is calculated by using the approximate model characterizing the molecular rotational behavior,and also provides a new research paradigm for solving macro thermodynamic quantities based on micro statistical processes.