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Ground state rotational spectra of the three isotopomers (CH2)2O...H35Cl, (CH2)2O...H37Cl, and (CH2)2O...D35Cl of a short-lived hydrogen-bonded dimer have been detected in the reactive mixture of oxirane and hydrogen chloride by using a fast-mixing nozzle in conjunction with a Balle–Flygare Fourier-transform microwave spectrometer. Rotational constants, centrifugal distortion constants and Cl-nuclear quadrupole coupling constants were determined for each isotopomer. In particular, all four components χaa, χbb, χcc, and χac of the coupling tensor were obtained. A detailed analysis of the rotational constants allows the conclusion that the dimer has Cs symmetry, with a steeply pyramidal arrangement completed at oxygen by the hydrogen bond with HCl. Diagonalization of the complete Cl-nuclear quadrupole coupling tensor leads to the principal axis components χxx, χyy, and χzz (where z is the HCl direction in the dimer). The angle of rotation α is the angle between the HCl (z) direction and the a-axis direction in the equilibrium conformation of the dimer. It is larger by ∼10° than the angle γ between the O...Cl internuclear line and the principal inertial axis a in each case and implies that the hydrogen bond is bent by 180-θ=∼16.5° from the collinear arrangement O...H–Cl (θ=0). The angle 180-θ and the angle [lowercase_phi_synonym]=76.2° made by the O...Cl internuclear line with the extension of the oxirane local C2 axis are interpreted in terms of a simple model of the hydrogen bond. [ABSTRACT FROM AUTHOR]

The ground-state rotational spectra of the symmetric-top isotopomers [(CH3)314N, H35Cl], [(CH3)314N, D35Cl], [(CH3)315N, H35Cl], and [(CH3)315N, H37Cl] of a dimer formed between trimethylamine and hydrogen chloride have been observed in the vapor above heated samples of solid trimethylammonium chloride by pulsed-nozzle, Fourier-transform, microwave spectroscopy. Spectroscopic constants have been determined in each case and for [(CH3)314N, H35Cl] the values are B0=1800.4605(2) MHz, DJ=0.320(10) kHz, DJK=13.59(11) kHz, χ(35Cl)=-21.625(5) MHz, and χ(14N)=-3.504(5) MHz. The observed rotational constants B0 indicate that the nuclei N, H, and Cl lie along the C3 symmetry axis of the molecule in the order N···H···Cl with the distance r(N···Cl)=2.8164(3) Å. A comparison of the values of the nuclear quadrupole coupling constants χ(35Cl) and χ(14N) with those in related dimers and molecules leads to the evocation of some ionic character (CH3)3N +H Cl arising from a significant extent of proton transfer from Cl to N. This conclusion is reinforced when the values of χ(35Cl) and χ(14N) predicted on the basis of a recent electrostatic hydrogen-bonded model (CH3)3N···HCl of the dimer are considered. The intermolecular stretching force constants kσ=84(3) N m-1 determined from DJ has a magnitude closer to that expected in the ion-pair limit than in the hydrogen-bond limit. [ABSTRACT FROM AUTHOR]

The pure rotational spectra of the four isotopomers 84Kr...H 35Cl, 84Kr...H 37Cl, 86Kr...H 35Cl, and 84Kr...D 35Cl of the van der Waals complex of krypton and hydrogen chloride have been observed in the vibrationally excited state (1000) by incorporating a pulsed glow-discharge source of excited-state molecules into a conventional pulsed-nozzle Fourier-transform microwave spectrometer. The rotational constant B1, the centrifugal distortion constant D1, and the Cl nuclear quadrupole coupling constant χ1(Cl) are reported for each isotopomer. The time of flight of the (1000) Kr...HCl molecules between the region of vibrational excitation and the detection region of the spectrometer indicates that the vibrational predissociative lifetime of the state (1000) is τ≥400 μs. Molecular properties of (1000) Kr...HCl determined from the observed spectroscopic constants are compared with those previously available for the ground state. [ABSTRACT FROM AUTHOR]