Search

Pure rotational spectra of the ground electronic-vibrational X1 state of 204Pb19F, 206Pb19F, 207Pb19F, and 208Pb19F are measured with a resonator pulsed supersonic jet Fourier-transform microwave spectrometer. Also reported is a new measurement of the Stark effect on the optical spectra of A←X1 transitions. These spectra are combined with published high-resolution infrared spectra of X2↔X1 transitions in order to create a complete picture of the ground state of lead monofluoride. For the microwave data, molecules are prepared by laser ablation of lead target rods and stabilized in a supersonic jet of neon mixed with sulfur hexafluoride. For the optical Stark spectra, a continuous source of molecules is created in a nozzle heated to 1000 °C. The microwave spectra confirm, improve, and extend previously reported constants that describe the rotational, spin-orbit, and hyperfine interactions of the ground electronic state of the PbF molecule. A discrepancy concerning the sign of the hyperfine constant describing the 207Pb nucleus is discussed. Magnetic-field-dependent microwave spectra are used to characterize the Zeeman interaction in terms of two g factors of the body-fixed electronic wave function. The optical Stark spectra are used to characterize the electric dipole moment of the X1 and A states. [ABSTRACT FROM AUTHOR]

The molecular structures of SeSCH32and TeSCH32were investigated using gas-phase electron diffraction GED and ab initioand DFT geometry optimisations. While parameters involving H atoms were refined using flexible restraints according to the SARACEN method, parameters that depended only on heavy atoms could be refined without restraints. The GED-determined geometric parameters rh1 are: rSe–S 219.11, rS–C 183.21, rC–H 109.64 pm; ∠S–Se–S 102.93, ∠Se–S–C 100.62, ∠S–C–H mean 107.45, S–Se–S–C 87.920, Se–S–C–H 178.819° for SeSCH32, and rTe–S 238.12, rS–C 184.13, rC–H 110.06 pm; ∠S–Te–S 98.96, ∠Te–S–C 99.74, ∠S–C–H mean 109.29, S–Te–S–C 73.048, Te–S–C–H 180.119° for TeSCH32. Ab initioand DFT calculations were performed at the HF, MP2 and B3LYP levels, employing either full-electron basis sets 3-21Gd or 6-31Gd or an effective core potential with a valence basis set LanL2DZd. The best fit to the GED structures was achieved at the MP2 level. Differences between GED and MP2 results for rS–C and ∠S–Te–S were explained by the thermal population of excited vibrational states under the experimental conditions. All theoretical models agreed that each compound exists as two stable conformers, one in which the methyl groups are on the same side gg−conformer and one in which they are on different sides ggconformer of the S–Y–S plane Y Se, Te. The conformational composition under the experimental conditions could not be resolved from the GED data. Despite GED R-factors and ab initioand DFT energies favouring the ggconformer, it is likely that both conformers are present, for SeSCH32as well as for TeSCH32.

The series of compounds ButX₂SiSiX₂But (X = Cl, Br and I) have been studied by X-ray crystallography, vibrational spectroscopy and ab initio calculations. The solids were all found to be anti and the vibrational spectra are consistent with this observation. The molecular structure of 1,2-di-tert-butyltetrachlorodisilane, ButCl₂SiSiCl₂But, has also been determined in the gas phase by electron diffraction (GED) and ab initio molecular-orbital calculations. The conformation is distorted slightly from the fully staggered arrangement, with φ(CSiSiC) 167.7(11)°. Important structural parameters (r_a) include: Si–Si 238.0(7) pm, Si–C 187.2(7) pm, C–C 154.3(2) pm, C–H 114.2(4) pm, Si–Si–C 119.8(6)°, Cl–Si–Cl 105.5(8)° and C–Si–Si–C 167.7(11)°. These experimental observations are supported by theoretical predictions obtained at the MP2/6-31G* level.

Here we report precision microwave spectroscopy of pure rotational transitions of the 207Pb19F isotopologue. We use these data to make predictions of the sensitivity of the molecule to P-odd, T-even and P-odd, T-odd effects. [ABSTRACT FROM AUTHOR]