Campargue Alain, Solodov Alexander M, Solodov Alexander A, Yachmenev Andrey, Yurchenko Sergei N
Univ. Grenoble Alpes, CNRS, LIPhy, 38000 Grenoble, France.
Laboratory of Molecular Spectroscopy, V. E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, 1, Academician Zuev sq., 634055, Tomsk, Russia.
Phys Chem Chem Phys. 2020 Jun 10;22(22):12476-12481. doi: 10.1039/d0cp01667e.
Nowadays, the spectroscopic databases used for the modeling of Earth and planetary atmospheres provide only electric-dipole transitions for polyatomic molecules (H2O, CO2, N2O, CH4, O3…). Very recently, electric-quadrupole transitions have been detected in the high sensitivity cavity ring down spectrum (CRDS) of water vapour near 1.3 μm [A. Campargue et al., Phys. Rev. Res., 2020, 2, 023091, DOI: 10.1103/PhysRevResearch.2.023091]. This discovery paved the way to systematic searches of quadrupole transitions in water vapor and other polyatomic molecules. In the present work, on the basis of high accuracy ab initio predictions, H216O quadrupole lines are detected for the first time in the 5.4 μm and 2.5 μm regions where they are predicted to have their largest intensities (up to 10-26 cm per molecule). A total of twelve quadrupole lines are identified in two high sensitivity Fourier transform spectra recorded with a 1064 m path length. Ten lines in the 4030-4150 cm-1 region are assigned to the ν3 band while the lines near 1820 and 1926 cm-1 belong to the ν2 band. The derived line intensities which are largely above the dipole intensity cut-off of the standard spectroscopic databases, agree nicely with the theoretical predictions. We thus conclude that the calculated line list of quadrupole transitions, validated by the present measurements, should be incorporated in the spectroscopic databases.
如今，用于地球和行星大气建模的光谱数据库仅提供多原子分子（H₂O、CO₂、N₂O、CH₄、O₃……）的电偶极跃迁。最近，在1.3μm附近的水蒸气高灵敏度腔衰荡光谱（CRDS）中检测到了电四极跃迁 [A. Campargue等人，《物理评论研究》，2020年，2，023091，DOI: 10.1103/PhysRevResearch.2.023091]。这一发现为系统搜索水蒸气和其他多原子分子中的四极跃迁铺平了道路。在本工作中，基于高精度的从头算预测，首次在5.4μm和2.5μm区域检测到H₂¹⁶O四极谱线，预计这些区域的谱线强度最大（高达每分子10⁻²⁶cm）。在两条路径长度为1064m的高灵敏度傅里叶变换光谱中总共识别出了12条四极谱线。4030 - 4150cm⁻¹区域的10条谱线属于ν₃带，而1820和1926cm⁻¹附近的谱线属于ν₂带。推导得到的谱线强度远高于标准光谱数据库的偶极强度截止值，与理论预测吻合良好。因此我们得出结论，经本测量验证的四极跃迁计算谱线列表应纳入光谱数据库。
