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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: The pure rotational spectrum of CHF2I has been recorded for the first time, in a supersonic expansion in the region 1.7–17GHz, and at room-temperature in the region 302–318GHz. The observed transitions span the values of from 0 up to 67. Precise rotational and centrifugal distortion constants have been determined. Furthermore, the complete iodine nuclear electric quadrupole coupling tensor, in the inertial and principal axes, has been determined. Quantum chemical calculations have been performed to aid with the analysis. Iodine quadrupole mediated perturbations have resulted in the following observations: (i) several transitions having enhanced intensities and (ii) the observation of several forbidden, , transitions. Comparisons in electronic structure are made between the series of molecules ; and X=Cl, Br, I. [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: 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]

Abstract: The first far-infrared high resolution absorption measurement of the cis-methyl nitrite molecule has been recorded in the range 15–400cm−1 using the synchrotron AILES beamline radiation at SOLEIL with a resolution of 0.0011cm−1. First assignments for the pure rotational transitions (15–65cm−1) belonging to the ground νt (=ν 15)=0 and first νt =1 excited torsional state are based on measurements from previous studies performed in the 13–40GHz spectral range, as well as on new millimeter-wave measurements performed at Lille in the spectral range 75–465GHz. A few measurements and remeasurements in the 1.8–13GHz were also performed using the chirped FT-MW spectrometer located in North Texas. The pure rotational transitions in the far-infrared and in the microwave spectral range belonging to the two first torsional states have been globally fitted using the RAM (“Rho Axis Method”) dealing with the rotation–torsion Hamiltonian and implemented in the BELGI code. A total of 708 and 713 microwave transitions (6⩽ J ⩽40, ⩽23) belonging to the ground torsional state νt =0 and 1 have been fitted with root-mean-square (rms) deviations of 37.4kHz and 32.3kHz respectively, and 3170 pure rotational transitions in the far-infrared range (12⩽ Jmax ⩽65, 0⩽ ⩽48) belonging to νt =0 and 1 have been fitted with a rms deviation of 0.00017cm−1, using 35 parameters. Since in the far-infrared spectral range, the A–E internal rotor splittings have not been observed for the transitions belonging to the torsional ground νt =0 state of the cis-methyl nitrite species, another fit was performed on those lines, using a Watson type Hamiltonian for comparison. [Copyright &y& Elsevier]