Search

Abstract: A chirped pulse Fourier transform microwave spectrometer was used to obtain pure rotational spectra for CF3CF2Cl between 8GHz and 16GHz, and for CF3CF2Br between 8GHz and 14GHz. In both cases rotational constants, quartic centrifugal distortion constants and chlorine/bromine nuclear electric quadrupole coupling tensors were obtained for the first time. For both compounds only the trans conformer was observed. Quantum chemical calculations have provided structures with rotational constants closely matching the experimental values. For CF3CF2Br the spectra collected were sufficiently strong that the C-13 isotopologues could be observed in natural abundance. ΔJ =2 transitions were observed in the rotational spectrum of CF3CF2Br, but were not observed in the spectrum for CF3CF2Cl. [Copyright &y& Elsevier]

Abstract: The pure rotational spectrum of perfluorobutyryl fluoride, C3F7COF, was measured using a pulsed nozzle, chirped pulse Fourier transform microwave spectrometer. A total of 280 transitions for the only observed conformer were recorded and analyzed. The rotational constants are A =1397.4330(1)MHz, B =619.17456(8)MHz, and C =592.06831(8)MHz. Quantum chemical calculations and the spectral analysis indicate that the observed conformer is the skew–anti form with calculated dihedral angles CCCO=120°, and CCCC≈170°. Conformational differences between perfluorobutyryl fluoride, perfluorobutyryl chloride, butyryl fluoride and butyryl chloride are discussed. [Copyright &y& Elsevier]

Abstract: A chirped pulse Fourier transform microwave spectrometer has been used to record the pure rotational spectrum of perfluorobutyryl chloride seeded in a pulsed supersonic expansion of argon gas. Only one conformer of the title molecule was observed. For the 35Cl species a total of 236 spectral transitions were recorded. Quantum chemical calculations together with the spectral constants obtained indicate that the observed conformer has the CCCCOCl centers contained within the ab plane with a dihedral angle ∠CCCO=0°. [Copyright &y& Elsevier]

Abstract: A search accelerated correct intensity Fourier transform microwave (SACI-FTMW) spectrometer has been used to rapidly record the rotational spectrum of pivaloyl chloride between 8 and 18GHz. Both a radio frequency and regular cavity-based instrument have then been used to obtain high resolution measurements below 4GHz and in the 4–18GHz regions, respectively. Rotational constants, centrifugal distortion constants, and chlorine nuclear quadrupole coupling constants have been determined for both the 35Cl and 37Cl isotopologues. The spectrum provides no evidence concerning internal rotation in the molecule. [Copyright &y& Elsevier]

Abstract: Tin metal has been ablated with pulsed radiation from a Nd:YAG laser ( nm). Carbonyl sulfide, diluted in high pressure argon, has been pulsed into the resultant Sn plasma. One of the results of this experiment has been the production of SnS. These events have allowed a rotational spectrum of tin monosulfide to be studied using a chirped-pulse Fourier transform microwave spectrometer. The resolution of the spectrum obtained was sufficient to observe hyperfine structure from the 117Sn and 119Sn-containing SnS molecules. Tin nuclear spin-rotation hyperfine constants are reported for the first time. [Copyright &y& Elsevier]

Abstract: A Fourier transform microwave spectrometer has been used to make high resolution measurements on the J =1–0 rotational transition for 11 isotopomers of SnO. For the most abundant isotopomer the transition was observed in the v =0,1,2,and 3 states. Magnetic hyperfine structure was observed in the transitions for 115Sn16O, 117Sn16O and 119Sn16O. The nuclear spin-rotation constant C I (Sn) has been determined for these isotopomers for the first time and these constants have been related to nmr shielding parameters. A multi-isotopomer analysis, including data from the 120Sn17O and 120Sn18O isotopomers, has been performed on the data. Born–Oppenheimer breakdown parameters were required in the fit and these parameters have been compared to those for the other Sn-chalcogenides. [Copyright &y& Elsevier]

Abstract: New molecular structural data is presented for a cyanide terminated oligomer of polytetrafluoroethene. The target molecule, CF3–(CF2)6–CN, has been seeded within a pulsed supersonic expansion of argon. The result of this action is to cool the species to rotational temperatures below 4K. Within this state, the pure rotational spectrum of the oligomer has been recorded using two types of Fourier transform microwave spectroscopy. A total of 111 transitions have been identified involving rotational J levels between 6 and 40. Only a- and b-type transitions were observed. The spectrum has been analyzed using a Hamiltonian containing all three rotational constants and one centrifugal distortion constant, D J . The experimental spectroscopic constants have been used to develop an effective molecular structure by scaling the quantum chemical calculated structure. The data shows that the seven carbon perfluorinated chain for the isolated oligomer twists ≈104°. This compares well to the C7F13-twist of ≈97° anticipated from the X-ray structure of phase II polytetrafluoroethene. [Copyright &y& Elsevier]