Brünken Sandra, Müller Holger S P, Lewen Frank, Giesen Thomas F
I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany.
J Chem Phys. 2005 Oct 22;123(16):164315. doi: 10.1063/1.2074467.
We present an analysis of a global, field-free data set of the methylene radical CH2 in its X 3B1 vibronic ground state by means of a novel Euler expansion of the Hamiltonian. The data set comprises pure rotational transitions up to 2 THz obtained with microwave accuracies of 30-500 kHz as well as nu2 ground-state combination differences and pure rotational data obtained with infrared accuracies of 0.001-0.010 cm(-1). Highly accurate spectroscopic parameters have been determined. These include rotational, spin-spin, spin-rotation, and electron-spin-nuclear-spin coupling terms along with several centrifugal distortion corrections. The spectroscopic model has been tested and improved by recording newly three weak DeltaN not equalDeltaJ fine-structure components of the N(KaKc)=2(12)-3(03) and 5(05)-4(14) transitions near 434, 454, and 581 GHz. These lines were rather close to the predictions. Overall weighted root mean squares of 1.28 and 0.83 were achieved for fits in which the Euler expansion was used only for the rotational part of the Hamiltonian or for the rotational and spin-spin terms of the Hamiltonian, respectively. The resulting spectroscopic parameters allow for precise frequency predictions of astrophysically important rotational transitions of methylene.
我们通过哈密顿量的一种新型欧拉展开，对处于X 3B1振转基态的亚甲基自由基CH2的全球无场数据集进行了分析。该数据集包括高达2太赫兹的纯转动跃迁，其微波精度为30 - 500千赫兹，以及ν2基态组合差和红外精度为0.001 - 0.010厘米−1的纯转动数据。已经确定了高精度的光谱参数。这些参数包括转动、自旋 - 自旋、自旋 - 转动以及电子 - 自旋 - 核自旋耦合项，还有几个离心畸变校正项。通过新记录434、454和581吉赫兹附近N(KaKc)=2(12)-3(03)和5(05)-4(14)跃迁的三条微弱的ΔN≠ΔJ精细结构分量，对光谱模型进行了测试和改进。这些谱线与预测结果相当接近。在分别仅将欧拉展开用于哈密顿量的转动部分或哈密顿量的转动和自旋 - 自旋项的拟合中，总体加权均方根分别达到了1.28和0.83。所得的光谱参数能够对亚甲基在天体物理学上重要的转动跃迁进行精确的频率预测。
