The pure rotational spectrum of the ZnCCH (X̃ 2Σ +) 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, 64ZnCCH, and between 4 and 10 for the 66ZnCCH, 68ZnCCH, 64ZnCCD, and 64Zn 13C 13CH 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 2Σ Hamiltonian, and rotational, spin-rotation, and H, D, and 13C 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 2Π state may exist ∼19 000 cm -1 in energy above the ground state.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry