Department of Chemistry and Biochemistry, 933 North Cherry Avenue, University of Arizona, Tucson, Arizona 85721, USA.
J Chem Phys. 2012 Jun 28;136(24):244310. doi: 10.1063/1.4729943.
The pure rotational spectrum of the ZnCCH (X̃(2)Σ(+)) radical has been measured using Fourier transform microwave (FTMW) and millimeter direct-absorption methods in the frequency range of 7-260 GHz. This work is the first study of ZnCCH by any type of spectroscopic technique. In the FTMW system, the radical was synthesized in a mixture of zinc vapor and 0.05% acetylene in argon, using a discharge assisted laser ablation source. In the millimeter-wave spectrometer, the molecule was created from the reaction of zinc vapor, produced in a Broida-type oven, with pure acetylene in a dc discharge. Thirteen rotational transitions were recorded for the main species, (64)ZnCCH, and between 4 and 10 for the (66)ZnCCH, (68)ZnCCH, (64)ZnCCD, and (64)Zn(13)C(13)CH isotopologues. The fine structure doublets were observed in all the data, and in the FTMW spectra, hydrogen, deuterium, and carbon-13 hyperfine splittings were resolved. The data have been analyzed with a (2)Σ Hamiltonian, and rotational, spin-rotation, and H, D, and (13)C hyperfine parameters have been established for this radical. From the rotational constants, an r(m) ((1)) structure was determined with r(Zn-C) = 1.9083 Å, r(C-C) = 1.2313 Å, and r(C-H) = 1.0508 Å. The geometry suggests that ZnCCH is primarily a covalent species with the zinc atom singly bonded to the C≡C-H moiety. This result is consistent with the hyperfine parameters, which suggest that the unpaired electron is localized on the zinc nucleus. The spin-rotation constant indicates that an excited (2)Π state may exist ∼19,000 cm(-1) in energy above the ground state.
锌烯丙基氰化物（X̃(2)Σ(+))自由基的纯旋转光谱已通过傅里叶变换微波（FTMW）和毫米直接吸收方法在 7-260 GHz 的频率范围内进行了测量。这是首次使用任何类型的光谱技术对 ZnCCH 进行的研究。在 FTMW 系统中，自由基是在锌蒸气和 0.05%乙炔的混合物中，使用放电辅助激光烧蚀源合成的。在毫米波光谱仪中，分子是由 Broida 型烤箱中产生的锌蒸气与纯乙炔在直流放电中反应生成的。记录了主要物种 (64)ZnCCH 的 13 个旋转跃迁，以及 (66)ZnCCH、(68)ZnCCH、(64)ZnCCD 和 (64)Zn(13)C(13)CH 同位素的 4 到 10 个跃迁。所有数据中都观察到精细结构双峰，在 FTMW 光谱中，还解析了氢、氘和碳-13 超精细分裂。这些数据已用 (2)Σ哈密顿量进行了分析，并确定了该自由基的旋转、自旋-旋转和 H、D 和 (13)C 超精细参数。从旋转常数确定了 r(m) ((1))结构，r(Zn-C) = 1.9083 Å，r(C-C) = 1.2313 Å，r(C-H) = 1.0508 Å。该结构表明 ZnCCH 主要是一个共价物种，锌原子与 C≡C-H 部分单键连接。这一结果与超精细参数一致，表明未配对电子定域在锌原子核上。自旋-旋转常数表明，在基态上方约 19000 cm(-1)的能量处可能存在激发的 (2)Π 态。
