MICROWAVE DETECTION OF PROTONATED SO2_2 IN TWO ISOMERIC FORMS

Author Institution: Harvard-Smithsonian Center for Astrophysics, 60 Garden St.; Cambridge, MA 02138, and School of Engineering \& Applied Sciences, Harvard University, 29 Oxford St., Cambridge, MA 02138; Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, 53121 Bonn, GermanyBy means of Fabry-Perot FT microwave spectroscopy, the rotational spectrum of protonated sulfur dioxide in two distinct isomeric forms, a \textit{cis} and a \textit{trans} geometry, is reported. Searches for both isomers were based on theoretical structures obtained at the CCSD(T)/cc-pwCVQZ level of theory corrected for zero-point vibrational effects at the CCSD(T)/cc-pV(T+$d$)Z level. At a similarly high level of theory, the \textit{cis} isomer is calculated to be the global minimum on the potential energy surface, but the \textit{trans} isomer is predicted to lie only a few kcal/mol higher in energy. The identification of \textit{cis} HOSO$^+$ has been confirmed by detection of rotational lines of DOSO$^+$ and HO$^{34}$SO$^+$ at precisely the expected frequency shifts. Because sulfur dioxide is a well known interstellar and extragalactic species, and because it possesses a large proton affinity, HOSO$^+$ is a excellent candidate for radioastronomical detection

TIMASSS: The IRAS16293-2422 Millimeter And Submillimeter Spectral Survey. I. Observations, calibration and analysis of the line kinematics

While unbiased surveys observable from ground-based telescopes have previously been obtained towards several high mass protostars, very little exists on low mass protostars. To fill up this gap, we carried out a complete spectral survey of the bands at 3, 2, 1 and 0.8 mm towards the solar type protostar IRAS16293-2422. The observations covered about 200\,GHz and were obtained with the IRAM-30m and JCMT-15m telescopes. Particular attention was devoted to the inter-calibration of the obtained spectra with previous observations. All the lines detected with more than 3 sigma and free from obvious blending effects were fitted with Gaussians to estimate their basic kinematic properties. More than 4000 lines were detected (with sigma \geq 3) and identified, yielding a line density of approximatively 20 lines per GHz, comparable to previous surveys in massive hot cores. The vast majority (~2/3) of the lines are weak and due to complex organic molecules. The analysis of the profiles of more than 1000 lines belonging 70 species firmly establishes the presence of two distinct velocity components, associated with the two objects, A and B, forming the IRAS16293-2422 binary system. In the source A, the line widths of several species increase with the upper level energy of the transition, a behavior compatible with gas infalling towards a ~1 Mo object. The source B, which does not show this effect, might have a much lower central mass of ~0.1 Mo. The difference in the rest velocities of both objects is consistent with the hypothesis that the source B rotates around the source A. This spectral survey, although obtained with single-dish telescope with a low spatial resolution, allows to separate the emission from 2 different components, thanks to the large number of lines detected. The data of the survey are public and can be retrieved on the web site http://www-laog.obs.ujf-grenoble.fr/heberges/timasss.Comment: 41 pages (26 pages of online Tables), 7 Tables and 6 Figure

{Millimeter Multiplicity in NGC 6334 I and I(N)

Using the Submillimeter Array (SMA), we have imaged the 1.3 millimeter continuum emission at the center of the massive star-forming regions NGC 6334 I and I(N). In both regions, the SMA observations resolve the emission into multiple millimeter sources, with most of the sources clustered into areas only 10,000 AU in diameter. Toward NGC 6334 I, we find four compact sources: the two brightest (I-SMA1 and I-SMA2) are associated with previously-known ammonia cores; I-SMA3 is coincident with the peak of the compact HII region (NGC 6334 F); and I-SMA4 is a newly-discovered object. While I-SMA3 exhibits a mixture of free-free and dust emission, the rest of the objects are dust cores. Toward NGC 6334 I(N), seven compact dust cores are found, one of which is associated with a faint centimeter source. With the exception of I-SMA3, none of the millimeter sources have infrared counterparts in Spitzer Space Telescope 3-8 micron images. Using a simple physical model for the dust continuum emission, the estimated mass of interstellar material toward each of these compact objects is in the range of 3 to 66 solar masses. The total mass in the compact objects appears to be similar in I and I(N). The small size of these groups of sources suggest that these objects are proto-Trapezia forming in the centers of clusters of low to intermediate-mass stars.Comment: 6 pages, 3 figures, to appear in The Astrophysical Journa

Discovery of H2_2CCCH+^+ in TMC-1

Based on a novel laboratory method, 14 mm-wave lines of the molecular ion H$_2$CCCH$^+$ have been measured in high resolution, and the spectroscopic constants of this asymmetric rotor determined with high accuracy. Using the Yebes 40 m and IRAM 30 m radio telescopes, we detect four lines of H$_2$CCCH$^+$ towards the cold dense core TMC-1. With a dipole moment of about 0.55 Debye obtained from high-level ab initio calculations, we derive a column density of 5.4$\pm$1$\times$10$^{11}$ cm$^{-2}$ and 1.6$\pm$0.5$\times$10$^{11}$ cm$^{-2}$ for the ortho and para species, respectively, and an abundance ratio N(H$_2$CCC)/N(H$_2$CCCH$^+$)= 2.8$\pm$0.7. The chemistry of H$_2$CCCH$^+$ is modelled using the most recent chemical network for the reactions involving the formation of H$_2$CCCH$^+$. We find a reasonable agreement between model predictions and observations, and new insights into the chemistry of C$_3$ bearing species in TMC-1 are obtained

Phosphorus and silicon analogs of isocyanic acid: Microwave detection of HPCO and HNSiO

Phosphaketene, HPCO, and silaisocyanic acid, HNSiO, have been characterized in the gas phase for the first time, employing Fourier transform microwave spectroscopy. Besides the parent isotopic species, the rare isotopologs (HPCO)-C-13, (HNSiO)-Si-29, and (HNSiO)-Si-30 were also observed. The molecular parameters derived experimentally agree very well with results of new quantum-chemical calculations performed at the coupled-cluster level of theory. Other derivatives of HNCO, in which one atom is replaced with its third-row counterpart, or two atoms are replaced with their second-row counterparts, may be detectable using the same combined theoretical/experimental approach. Because both isocyanic acid, HNCO, and its sulfur variant HNCS are abundant in molecule-rich astronomical sources, HPCO and HNSiO are good candidates for future radio astronomical searches. (C) 2015 Elsevier Inc. All rights reserved

HIGH-RESOLUTION INFRARED SPECTROSCOPY OF Ge2_2C3_3

Author Institution: I. Physikalisches Institut, Universitat zu Koln, 50937 Koln, Germany; Universitat Kassel, Fachbereich 10 - Physik, 34132 Kassel, Germany; Institut fur Physikalische Chemie, Universitat Mainz, 55099 Mainz, GermanyCarbon-rich systems are of great importance in diverse areas of research like material science as well as astro- and structural chemistry. Despite this relevance, our knowledge of smaller cluster units is still fragmentary, particularly with respect to investigations at high-spectral resolution in the gas phase. Unequivocal assignment of spectral features to their molecular carriers is critically dependent on predictions from high-level quantum-chemical calculations. In turn, high-resolution studies provide useful information to assess the predictive power of quantum-chemical methods. This is particularly interesting for cluster systems harboring heavy elements for which so far relatively little is known from experiment. With this contribution, we would like to present a recent gas-phase study of a polyatomic germanium-carbon cluster, linear Ge$_2$C$_3$ (Ge=C=C=C=Ge), which was previously studied in an Ar matrix \textbf{114}, 3570 (2001).}. The cluster was produced through laser ablation of germanium-graphite sample rods and observed in a free jet at wavelengths around 5$\mu$m. Additionally, quantum-chemical calculations of Ge$_2$C$_3$ were performed at the CCSD(T) level of theory. The production and observation of Ge$_2$C$_3$ suggests that many more binary clusters should be amenable to high-resolution spectroscopic techniques not only in the infrared but also in the microwave region

Laboratory Astrochemistry in the Infrared: High-Resolution Spectroscopy and Molecular Structure of Carbon-Silicon Clusters

A new high-resolution infrared spectrometer using an optical parametric oscillator working at 5 μm as radiaton source has been assembled in the Cologne laboratory and is now operated routinely. As one of the first projects, we have reobserved the ν3 vibrational fundamental (asymmetric C-C stretching mode) of Si2C3 located at 1968.2 cm-1

The rotational spectrum of protonated sulfur dioxide, HOSO+

Aims. We report on the millimeter-wave rotational spectrum of protonated sulfur dioxide, HOSO+. Methods. Ten rotational transitions between 186 and 347 GHz have been measured to high accuracy in a negative glow discharge. Results. The present measurements improve the accuracy of the previously reported centimeter-wave spectrum by two orders of magnitude, allowing a frequency calculation of the principal transitions to about 4 km s(-1) in equivalent radial velocity near 650 GHz, or one linewidth in hot cores and corinos. Conclusions. Owing to the high abundance of sulfur-bearing molecules in many galactic molecular sources, the HOSO+ ion is an excellent candidate for detection, especially in hot cores and corinos in which SO2 and several positive ions are prominent