Laboratoire de Physique des Lasers, Atomes et Molécules, CERLA, UMR CNRS 8523, Université Lille 1, 59655 Villeneuve d'Ascq Cedex, France.
J Phys Chem A. 2010 Apr 15;114(14):4776-84. doi: 10.1021/jp909323h.
Fourier-transform microwave and millimeter-wave spectra of the iodomethyl radical, CH(2)I, have been observed in the ground vibronic state in the frequency ranges 17-38 GHz and 200-610 GHz, respectively. The pi-electron radical was produced either by iodine abstraction from diiodomethane (CH(2)I(2)) or by hydrogen abstraction from iodomethane (CH(3)I). Seventy-three hyperfine resolved lines owing to the two hydrogen and to the iodine nuclei have been detected in the microwave region, including K(a) = 0 (ortho species) and K(a) = 1 (para species). No hyperfine splitting due to the hydrogen nuclei could be observed for the para species, directly confirming the planarity of the radical and that the ground electronic state is (2)B(1). More than 400 a-type transitions that span the values N' < or = 35, K(a) < or = 6, were detected. A global least-squares analysis of the measured lines was conducted and led to the determination of an exhaustive list of molecular constants. In particular, the sign of the Fermi-contact constant of iodine was unambiguously determined to be negative, which is opposite to that of the other monosubstituted halomethyl radicals. This work allowed a systematic comparison of the structural and bonding properties among the CH(2)X analogues (where X = F, Cl, Br, and I) owing to the hyperfine coupling constants of both the hydrogen and halogen nuclei.
已在基电子振动态下分别在 17-38GHz 和 200-610GHz 频率范围内观察到碘甲基自由基（CH(2)I）的傅里叶变换微波和毫米波光谱。该π电子自由基是通过二碘甲烷（CH(2)I(2)）中碘的提取或碘甲烷（CH(3)I）中氢的提取产生的。在微波区域检测到了 73 条归因于两个氢核和碘核的超精细分辨线，包括 K(a) = 0（邻位物种）和 K(a) = 1（对位物种）。对于对位物种，由于氢核未观察到超精细分裂，直接证实了自由基的平面性和基态电子态为 (2)B(1)。检测到超过 400 条跨越 N' <= 35、K(a) <= 6 的 a 型跃迁。对测量线进行了全局最小二乘分析，得出了分子常数的详尽列表。特别是，碘的费米接触常数的符号被明确确定为负，这与其他单取代卤代甲基自由基的符号相反。由于氢核和卤核的超精细耦合常数，这项工作允许对 CH(2)X 类似物（其中 X = F、Cl、Br 和 I）的结构和键合性质进行系统比较。
