Molecular opacities of <inline-formula><tex-math id="Z-20221003130318">\begin{document}$ {{\text{X}}^{2}}{\Sigma}_{\text{g}}^{+} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130318.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130318.png"/></alternatives></inline-formula>, A<sup>2</sup>Π<sub>u</sub> and <inline-formula><tex-math id="Z-20221003130305">\begin{document}$ {{\text{B}}^{2}}{\Sigma}_{\text{u}}^{+} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130305.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130305.png"/></alternatives></inline-formula> states of nitrogen cation
Authors: Chen Chen , Zhao Guo-Peng , Qi Yue-Ying , Wu Yong , Wang Jian-Guo ,   Institute of Modern Physics, Fudan University, Shanghai 200433, China,   College of Data Science, Jiaxing University, Jiaxing 314001, China,   National Key Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100088, China,   HEDPS, Center for Applied Physics and Technology, and College of Engineering, Peking University, Beijing 100871, China
Published: June 2022

The potential curves, spectroscopic constants and dipole moments for <inline-formula><tex-math id="Z-20221003130344">\begin{document}$ {{\text{X}}^{2}}{\Sigma}_{\text{g}}^{+} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130344.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130344.png"/></alternatives></inline-formula>, A<sup>2</sup>Π<sub>u</sub> and <inline-formula><tex-math id="Z-20221003130359">\begin{document}$ {{\text{B}}^{2}}{\Sigma}_{\text{u}}^{+} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130359.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_Z-20221003130359.png"/></alternatives></inline-formula> state of <inline-formula><tex-math id="M10">\begin{document}$ {\text{N}}_{2}^{+} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_M10.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_M10.png"/></alternatives></inline-formula> are calculated by the internal contraction multi reference configuration interaction (icMRCI) method, with Davidson correction taken into consideration. According to the results of molecular structures, we present the partition function in a temperature range of 100–40000 K and the opacities at different temperatures (295, 500, 1000, 2000, 2500, 5000 and 10000 K) under a fixed pressure of 100 atm. It is found that the populations of excited states increase with temperature increasing, as a result, the wavelength range of opacity also increases and band boundaries for different transitions gradually become obscure. In comparison with the cases of N<sub>2</sub> with the same pressure and temperature, significant discrepancies are found in the wavelength ranges and structures of opacity of <inline-formula><tex-math id="M1119">\begin{document}$ {\text{N}}_{2}^{+} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_M1119.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_M1119.png"/></alternatives></inline-formula> for the present work. The influence of temperature on the opacity of <inline-formula><tex-math id="M11">\begin{document}$ {\text{N}}_{2}^{+} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_M11.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20220734_M11.png"/></alternatives></inline-formula> is studied systematically in the present work, which is expected to provide theoretical and data support for astrophysics.