Millimeter-Wave and High-Resolution Infrared Spectroscopy of the Ground and 14 Vibrationally Excited States Lying Below 1300 cm–1 of Pyrazole

The gas-phase rotational spectrum from 85 to 750 GHz and high-resolution infrared (IR) spectrum (Canadian Light Source) of 1H-pyrazole have been analyzed for the ground and vibrationally excited states lying below 1300 cm–1. The analysis benefits from the simultaneous analysis of rotational and high-resolution IR transitions that cover the same approximate ranges of J and K. In total, over 4400 transitions for the ground state have been measured, assigned, and least-squares fit to complete sextic centrifugally distorted-rotor Hamiltonian models. The presented ground-state rotational spectrum provides the foundation for astronomical searches across most of the frequency range covered by modern radiotelescopes. Additionally, the rotational and high-resolution infrared transitions of the 11 lowest-energy fundamental and three lowest-energy combination states have been measured, assigned, and least-squares fit. The four lowest-energy fundamental states (ν21, ν20, ν19, and ν18) are sufficiently separated in energy that they can all be well-treated by single-state Hamiltonians across the entire measured spectrum. The next four lowest-energy fundamental states (ν17, ν16, ν15, and ν14) form a Coriolis-coupled tetrad of states that are fit to a four-state model with six Coriolis interactions. The remaining vibrationally excited states investigated in this work (ν13, ν12, ν11, ν21 + ν20, ν21 + ν19, and ν21 + ν18) are treated by effective Hamiltonians, owing to their complex anharmonic- and Coriolis-coupling interactions. The experimental spectroscopic constants and vibrational energies are compared to their computed values (CCSD(T)/cc-pCVTZ).本文对1H-吡唑(1H-pyrazole)在85至750 GHz范围内的气相转动光谱(gas-phase rotational spectrum)，以及加拿大光源(Canadian Light Source)采集的高分辨率红外(IR)光谱(high-resolution infrared (IR) spectrum)展开了系统分析，分析覆盖基态与波数低于1300 cm⁻¹的全部振动激发态。本次分析得益于对覆盖近似相同J和K量子数范围的转动光谱与高分辨红外光谱跃迁开展联合分析，总计已测量、指认超过4400条基态跃迁，并通过最小二乘拟合(least-squares fit)构建了完整的六次离心畸变转子哈密顿量(sextic centrifugally distorted-rotor Hamiltonian)模型。本文报道的基态转动光谱，可为现代射电望远镜(radiotelescopes)覆盖的绝大多数频率范围的天文搜索工作提供坚实基础。此外，本研究还测量、指认了11个最低能量基频态(fundamental states)与3个最低能量组合频态(combination states)的转动与高分辨红外跃迁，并完成了最小二乘拟合。四个最低能量的基频态（ν₂₁、ν₂₀、ν₁₉与ν₁₈）之间的能量差足够显著，因此在全部测量光谱范围内均可通过单态哈密顿量进行精准处理。后续四个最低能量基频态（ν₁₇、ν₁₆、ν₁₅与ν₁₄）构成科里奥利耦合四重态(Coriolis-coupled tetrad)，通过包含6个科里奥利相互作用的四态模型完成拟合。本研究中其余被考察的振动激发态（ν₁₃、ν₁₂、ν₁₁、ν₂₁+ν₂₀、ν₂₁+ν₁₉与ν₂₁+ν₁₈）由于存在复杂的非谐性与科里奥利耦合相互作用，因此采用有效哈密顿量(effective Hamiltonians)进行处理。最后，将实验测得的光谱常数(spectroscopic constants)与振动能量，与CCSD(T)/cc-pCVTZ理论水平下的计算值进行了对比。