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The rotational spectra of two small silicon sulfides, silanethione H2SiS and the disilicon sulfide ring Si2S, have been detected in the centimeter band by Fourier transform microwave spectroscopy of a molecular beam; lines of H2SiS were also observed in the millimeter band up to 377 GHz in a glow discharge. Precise rotational and centrifugal distortionconstants have been determined for the normal and a number of the more abundant rare isotopic species of both closed-shell molecules. Theoretical equilibrium (re) structures of H2SiS and Si2S were derived from coupled-cluster calculations that included triple and quadruple excitations, core correlation, and extrapolation to the basis-set limit. The re structures agree to within 5×10-4 Å and 0.1°with empirical equilibrium (reemp) structures derived from the experimental rotational constants, combined with theoretical vibrational and electronic corrections. Both H2SiS and Si2S are good candidates for radioastronomical detection in the circumstellar shells of evolved carbon-rich stars such as IRC+10216, because they are fairly polar and are similar in composition to the abundant astronomical molecule SiS. [ABSTRACT FROM AUTHOR]

Context. Thioformaldehyde is an abundant molecule in various regions of the interstellar medium. However, available laboratory data limit the accuracies of calculated transition frequencies in the submillimeter region, in particular for minor isotopic species. Aims. We aim to determine spectroscopic parameters of isotopologs of H2CS that are accurate enough for predictions well into the submillimeter region. Methods. We investigated the laboratory rotational spectra of numerous isotopic species in natural isotopic composition almost continuously between 110 and 377 GHz. Individual lines were studied for most species in two frequency regions between 566 and 930 GHz. Further data were obtained for the three most abundant species in the 1290−1390 GHz region. Results. New or improved spectroscopic parameters were determined for seven isotopic species. Quantum-chemical calculations were carried out to evaluate the differences between ground state and equilibrium rotational parameters to derive semi-empirical equilibrium structural parameters. Conclusions. The spectroscopic parameters are accurate enough for predictions well above 1 THz with the exception of H213 H 2 13 $ {\rm{H}}_2^{13} $ C34S where the predictions should be reliable to around 700 GHz. [ABSTRACT FROM AUTHOR]

The carbon chain molecules vinylcyanoacetylene and cyanovinylacetylene have been investigated between 8 and 41 GHz by Fourier transform microwave spectroscopy of a supersonic molecular beam. Owing to the high spectral resolution of the present technique, significantly more accurate rotational and centrifugal distortion constants have been derived for both molecules. In addition, the dipole moments have been calculated at the B3LYP/cc-pVTZ level of theory. Because these carbon chains are similar in structure and composition to known astronomical molecules and because of their high polarity, both species are good candidates for radioastronomical detection. [Copyright &y& Elsevier]

Abstract: The pure rotational spectrum of deuterium isocyanide (DNC) was recorded in the frequency range from approximately 680 to 1985GHz. Twenty-one new transitions in the vibrational ground and first excited bending states (01 e,f 0) have been assigned, namely R-branch transitions from J=9←8 to 25←24. In a least squares analysis of these new transition frequencies together with previously reported millimeter-wave data, spectroscopic parameters up to sextic order could be derived with high precision for both states. Furthermore, the ℓ-type doubling constant q and its centrifugal distortion terms q J and q JJ were obtained for the first excited bending state. [Copyright &y& Elsevier]

Abstract: We report the unequivocal identification of the r Q 3 branch of perdeutero oxadisulfane, DSOD, which has been produced in a discharge of D2S together with D2O. By employing the Cologne Terahertz Spectrometer, we have located the band center near 653GHz, in very close agreement with earlier results deduced from the r Q 0 and r Q 2 branches. The A 0, B 0, and C 0 rotational constants have been determined by carrying out an asymmetric rotor least squares fit with all presently available data, including new R- and P-branch lines. Both, b- and c-type transitions have been observed and the relative dipole moment μ c/μ b has been determined from relative line strengths. All results agree very well with quantum chemically calculated values. [Copyright &y& Elsevier]

We report the first spectroscopic detection of perdeuterated 1-oxadisulfane, DSOD, generated in a radio-frequency plasma of D2S and D2O. The chain molecule DSOD produces a perpendicular-type spectrum, with well-known spectral features encountered in previous studies of geometrically related molecules, such as compact Q-branches, which are clearly recognizable. The arrangement of the transitions shaping the Q-branches usually provides sufficient proof for a clear-cut detection of a chain molecule such as DSOD. Guided by quantum chemical calculations, we have located the band center of the rQ2-branch of DSOD in the frequency region near 466.5 GHz using the Cologne terahertz spectrometer. This rQ2-branch displays both b- and c-type spectra, quite analogous to the behavior of the corresponding rQ2-branch of HSOH. In addition, we have been able to detect an internal rotational splitting of ∼0.5 MHz for c-type transitions of the rQ0-branch, which lends independent support to our present assignment. From the measurements performed on Q-branches, we derive the following differences in rotational constants: A−(B+C)/2=93331.001(15) MHz, and (B−C)/4=172.95923(29) MHz, in excellent agreement with theoretical predictions. [Copyright &y& Elsevier]

• Cryogenic action spectroscopy is applied to astrochemical relevant hydrocarbon ions. • Broadband vibrational gas-phase spectra of the propargyl and cyclopropenium cations are recorded with FELIX. • First spectroscopic characterization of their perdeuterated variants. • The extracted vibrational band positions allow to benchmark quantum-chemical calculations. • Isomer-selective formation pathways are investigated. Gas phase vibrational spectra of [C 3 H 3 ]+ isomers and their fully deuterated isotopologues measured in a cryogenic 22-pole ion trap are presented. The widely tunable free electron laser for infrared experiments, FELIX, was employed to cover the frequency range 500–2400 cm−1, complemented with an OPO/OPA system covering 2800–3400 cm−1. Spectral assignments for both the linear and cyclic isomeric form (H 2 C 3 H+ and c-C 3 H 3 +, respectively) are made based on various high-level computational studies. The effect of ion source conditions and different precursors (allene and propargyl chloride) for the preferential production of a specific isomer is discussed. The perturbation of the vibrational band position due to complexation with neon in the recorded infrared-predissociation (IRPD) spectra are also reported in this study. [ABSTRACT FROM AUTHOR]