基于描述双核分子体系包含转动光谱常数Lv所在高阶项在内的跃迁能谱的经典表达式, 采用差分收敛法(DCM)的物理思想, 推导获得了求解双核分子体系P支跃迁谱线的另一解析表达形式。 对于某一双核分子体系的P支跃迁带, 新的谱线表达式仅需要11条精确的实验跃迁谱线就可以正确预言高激发振转态的谱线结构, 同时, 利用谱线展开系数C还可以进一步给出计算谱线的不确定度以更可靠地预言高激发振转态的跃迁谱线。 推导获得了相应的计算公式以正确获得对应跃迁带的转动光谱常数(Bv′, Bv″, Dv′, Dv″, Hv′, Hv″, Lv′, Lv″)。 应用新的谱线表达式, 对35Cl+2和35Cl37Cl+离子电子态A2Πu－X2Πg(Ω=1/2)跃迁体系(3, 7)跃迁带的P支跃迁谱线进行了详细研究, 获得的计算结果不但能完全重复已知的实验数据, 还获得了实验上未能获得的包含高激发振转态在内的跃迁谱线。 另外, 通过计算同时也得到了各跃迁带的高阶转动光谱常数。 该研究方法和计算结果为人们进一步正确认识Cl+2离子电子态的内部能级结构及物理化学的相关性质提供了更完整的参考数据。

An analytical formula is derived from conventional expression of transition spectra containing higher terms rovibrational spectral constants Lv based on the difference converging method (DCM), which can calculate the accurate P-branch spectral lines of rovibrational transitions in some diatomic molecules systems. Based on the DCM method, a group of eleven known experimental transition lines is needed and a set of expansion coefficients C is chosen to predict correct transitional spectra of high-lying rovibrational states for a P-branch transition band of a diatomic system. In this study, the transitional spectral lines of high-lying excited states which may not be available experimentally and the rotational spectral constants of the corresponding transition bands were obtained correctly by using the DCM method for the (3, 7) band of A2Πu-X2Πg(Ω=1/2) transiton of the 35Cl+2 and 35Cl37Cl+2 ions. The calculated data can provide a better reference for the further understanding of the internal structure and physical and chemical properties of electronic states of the Cl+2 ion.