Bailleux Stéphane, Dréan Pascal, Zelinger Zdenĕk, Civis Svatopluk, Ozeki Hiroyuki, Saito Shuji
Laboratoire de Physique des Lasers, Atomes et Molécules, UMR CNRS 8523, CERLA, Université de Lille 1, F-59655 Villeneuve d'Ascq CEDEX, France.
J Chem Phys. 2005 Apr 1;122(13):134302. doi: 10.1063/1.1862619.
The rotational spectra of the two isotopic species of the bromomethyl radical, CH2 79Br and CH2 81Br, have been observed in their ground electronic state 2B1 in the 180-470 GHz frequency region, corresponding to a-type transitions from N=8-7 to N=21-20. The radical was produced by hydrogen abstraction of methylbromide (CH3Br) either by chlorine or by fluorine atoms in a free space cell. Hyperfine structure due to the bromine nucleus has been resolved in the observed spectra, and the rotational constants as well as the fine and hyperfine interaction constants were accurately determined for both isotopomers. The inertial defect was determined to be 0.028 96(20) and 0.028 95(20) amu A(2), for CH2 79Br and CH2 81Br, respectively, suggesting a planar structure. By fixing the [angle]HCH bond angle at 124.5 degrees , an effective molecular structure can be derived as r0(CBr)=1.848 A and r0(CH)=1.084 A. A comparison of the molecular structure of various halogen-substituted methyl radicals with respect to the planarity of these radicals is discussed.
在180 - 470GHz频率区域内，观测到了溴甲基自由基的两种同位素物种CH₂⁷⁹Br和CH₂⁸¹Br在基电子态²B₁下的转动光谱，这对应于从N = 8 - 7到N = 21 - 20的a型跃迁。该自由基是在自由空间池中通过氯原子或氟原子从甲基溴（CH₃Br）夺取氢而产生的。在所观测的光谱中分辨出了由溴核引起的超精细结构，并精确测定了两种同位素异构体的转动常数以及精细和超精细相互作用常数。对于CH₂⁷⁹Br和CH₂⁸¹Br，惯性缺陷分别确定为0.02896(20)和0.02895(20) amu Ų，这表明其结构为平面结构。通过将∠HCH键角固定在124.5度，可以推导出有效分子结构为r₀(CBr)=1.848 Å和r₀(CH)=1.084 Å。文中还讨论了各种卤素取代甲基自由基的分子结构在这些自由基平面性方面的比较。
