The rotational spectrum of the fluorobenzene-argon complex has been studied in the microwave region between 7 and 18 GHz using a pulsed molecular beam microwave Fourier transform spectrometer. The rotational constants were found to be A = 1811.81369(11) MHz, B= 1105.12965(15) MHz, C = 901.84281(5) MHz, the centrifugal distortion constants are A } = 2.6886(17) kHz, A JK = 8.3761 (52) kHz A K = -8.278(5) kHz, <5, =0.65993(72) kHz, and ^ = 6.013(11) kHz. The argon atom is placed 3.55 A above the ring plane.

Eine Vorzugskonformation des intern hoch dynamischen Fluormethan‐Trifluormethan‐Molekülkomplexes folgt aus der Stabilisierung der beiden Untereinheiten durch drei schwache CH⋅⋅⋅F‐Wasserstoffbrücken und elektrostatische Dipol‐Dipol‐Wechselwirkungen. Die beiden Einheiten sind nicht starr fixiert, sondern weisen große Amplituden der Bewegung durch fast vollständig freies Drehen um ihre Symmetrieachsen auf (siehe Bild).

A highly integrated supersonic-jet Fourier-transform microwave spectrometer of coaxially oriented beam-resonator arrangement (COBRA) type, covering 2-20GHz, has been recently built at Chongqing University, China. Built up almost entirely in an NI PXIe chassis, we take the advantage of the NI PXIe-5451 Dual-channel arbitrary waveform generator and the PXIe-5654 RF signal generator to create a spectrometer with wobbling capacity for fast resonator tuning. Based on the I/Q modulation, associate with PXI control and sequence boards built at the Leibniz Universitat Hannover, the design of the spectrometer is much simpler and very compact. The Fabry-Pérot resonator is semi-confocal with a spherical reflector of 630 mm diameter and a radius of 900 mm curvature and one circulator plate reflector of 630 mm diameter. The vacuum is effectuated by a three-stage mechanical (two-stage rotary vane and roots booster) pump at the fore line of a DN630 ISO-F 20000 L/s oil-diffusion pump. The supersonic-jet expansion is pulsed by a general valve Series 9 solenoid valve which is controlled by a general valve IOTA one driver governed by the experiment-sequence generation. First molecular examples to illustrate the performance of the new setup will include OCS and CF 3 CHFCl.

We present quantum chemical calculations on the MP4(SDQ) level with basis sets of high local quality to determine the nuclear quadrupole coupling tensor of

We recorded the microwave spectrum of hexafluoropropanone between 7 and 15 GHz using a pulsed molecular beam microwave Fourier transform spectrometer. The rotational constants were determined to be A = 2181.71980(14) MHz, B= 1037.22930(7) MHz, C = 934.89233(8) MHz, the quartic centrifugal distortion constants are D'

The microwave spectrum of 4-methylisothiazole was assigned by means of a pulsed molecular beam microwave Fourier transform spectrometer. Analysis of the spectrum yielded the rotational constants A = 7370.642 (

We reinvestigated by microwave Fourier transform spectroscopy the rotational spectra of the axial and equatorial isotopomers of piperidine and N-deutero piperidine. The rotational, centrifugal, and nitrogen quadrupole coupling constants were improved, the deuterium quadrupole coupling constants were determined. The principal coupling tensor elements for nitrogen were estimated.

As a first example in a series of substituted thiiranes we present an investigation of the nuclear quadrupole coupling in 33 S-methylthiirane in natural abundance. The rotational and quadrupole coupling constants are: A = 11 599.0976 (18)