Halfen D T, Ziurys L M
Department of Chemistry, Department of Astronomy, Arizona Radio Observatory, and Steward Observatory, University of Arizona, Tucson, AZ 85721, USA.
J Chem Phys. 2005 Feb 1;122(5):54309. doi: 10.1063/1.1824036.
The pure rotational spectrum of the MnCl radical (X (7)Sigma(+)) has been recorded in the range 141-535 GHz using millimeter-submillimeter direct absorption spectroscopy. This work is the first time the molecule has been studied with rotational resolution in its ground electronic state. MnCl was synthesized by the reaction of manganese vapor, produced in a Broida-type oven, with Cl(2). Transitions of both chlorine isotopomers were measured, as well as lines originating in several vibrationally excited states. The presence of several spin components and manganese hyperfine interactions resulted in quite complex spectra, consisting of multiple blended features. Because 42 rotational transitions were measured for Mn(35)Cl over a wide range of frequencies with high signal-to-noise, a very accurate set of rotational, fine structure, and hyperfine constants could be determined with the aid of spectral simulations. Spectroscopic constants were also determined for Mn(37)Cl and several vibrationally excited states. The values of the spin-rotation and spin-spin parameters were found to be relatively small (gamma=11.2658 MHz and lambda=1113.10 MHz for Mn(35)Cl); in the case of lambda, excited electronic states contributing to the second-order spin-orbit interaction may be canceling each other. The Fermi contact hyperfine term was found to be large in manganese chloride with b(F)(Mn(35)Cl)=397.71 MHz, a result of the manganese 4s character mixing into the 12sigma orbital. This orbital is spsigma hybridized, and contains some Mn 4psigma character, as well. Hence, it also contributes to the dipolar constant c, which is small and positive for this radical (c=32.35 MHz for Mn(35)Cl). The hyperfine parameters in MnCl are similar to those of MnH and MnF, suggesting that the bonding in these three molecules is comparable.
利用毫米-亚毫米直接吸收光谱法，在141 - 535 GHz范围内记录了MnCl自由基（X (7)Σ⁺）的纯转动光谱。这项工作是首次在基电子态下对该分子进行具有转动分辨率的研究。MnCl是通过在布罗伊达型炉中产生的锰蒸气与Cl₂反应合成的。测量了两种氯同位素异构体的跃迁，以及源自几个振动激发态的谱线。多个自旋分量和锰超精细相互作用的存在导致光谱相当复杂，由多个混合特征组成。由于在很宽的频率范围内以高信噪比测量了Mn(³⁵)Cl的42个转动跃迁，借助光谱模拟可以确定一组非常精确的转动、精细结构和超精细常数。还确定了Mn(³⁷)Cl和几个振动激发态的光谱常数。发现自旋-转动和自旋-自旋参数的值相对较小（对于Mn(³⁵)Cl，γ = 11.2658 MHz，λ = 1113.10 MHz）；就λ而言，对二阶自旋-轨道相互作用有贡献的激发电子态可能相互抵消。发现费米接触超精细项在氯化锰中很大，b(F)(Mn(³⁵)Cl) = 397.71 MHz，这是锰4s特征混入12σ轨道的结果。该轨道是spσ杂化的，也包含一些Mn 4pσ特征。因此，它也对偶极常数c有贡献，该自由基的偶极常数c较小且为正（对于Mn(³⁵)Cl，c = 32.35 MHz）。MnCl中的超精细参数与MnH和MnF的相似，表明这三个分子中的键合具有可比性。
