The GBT PRebiotic Interstellar MOlecule Survey (PRIMOS) towards Sgr B2N is the deepest, most complete spectral line survey in the range of 300MHz - 49 GHz. PRIMOS enables astronomers, chemists, and biologists to test theories of molecular formation, the origins of organic chemistry and the molecular complexity and physical and kinematic structure of material in our Galaxy. To date, PRIMOS data have resulted in 14 refereed publications since 2007, demonstrating the power of centimeter wave spectroscopy for detecting new organic species and revealing the significance of non-LTE effects including maser amplification in the cm-wave spectra of organic molecules. The survey has additionally advertised molecular astrophysics in public lectures, summer undergraduate diversity programs, and high school student projects. While the GBT is the only telescope in the world capable of conducting the PRIMOS Survey, PRIMOS data couples with newly available broad-bandwidth telescopes including the Jansky Very Large Array and ALMA. Synergistic observations with ALMA will be necessary to fully characterize the spectra of molecular material and determine excitation mechanisms leading to observed line radiation. This presentation provides an overview of the PRIMOS program, highlights PRIMOS science, and describes how the entire astronomical community can obtain the data for their own research.

Nitriles form the most prolific family of molecules known in the ISM, and laboratory work shows that radical-driven chemistry can account for the formation of a diverse set of nitrile and imine molecules. Broadband reaction screening of nitrile chemistry in a pulsed discharge nozzle coupled to a chirped-pulse Fourier transform rotational spectrometer has enabled detections of several new interstellar species including E- and Z-ethanimine¹ and E-cyanomethanimine². The detections were made by direct comparisons of laboratory broadband rotational spectra with the Robert C. Byrd Green Bank Telescope (GBT) PRebiotic Interstellar MOlecule Survery (PRIMOS) survey towards Sgr B2(N), the most chemically complex interstellar region known. In order to probe nitrile chemistry in Sgr B2, we targeted low energy rotational transitions in the 18-21 GHz range of several nitriles with the Karl G. Jansky Very Large Array (VLA) at  ∼ 1 arcsecond resolution. The data indicate that most nitriles and nitrile derivatives are co-spatial with shell shaped continuum features thought to be expanding ionization fronts. The CH2CN radical and imine species in particular are NOT associated with the hot core known as the "Large Molecule Heimat", where most large organic molecules are thought to reside. This result suggests radical driven nitrile chemistry may be promoted by near-UV radiation in moderate density regions of molecular clouds, and the data will be useful for evaluating possible formation mechanisms.
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¹R.A. Loomis et al. Ap. J. L. 765(L9), 2013. ²D.P. Zaleski et al. Ap. J. L. 765(L10), 2013.

Two transitions of methanimine (CH2NH) have been mapped towards Sgr B2 using the Jansky Very Large Array (VLA) with 1.5 arcsecond resolution. The two targeted transitions are both between low-lying energy states at similar frequencies, yet one appears in absorption whereas the other is in emission with the same line profile. The VLA data reveals that the spatial distributions of the two transitions match and that they are NOT associated with the hot core toward Sgr B2(N). As compared to other molecular lines observed towards Sgr B2 at centimeter wavelengths, the CH2NH emission line is highly uncharacteristic, and the transitions exhibits non-thermal effects implying a population inversion. We discuss the non-thermal excitation of CH2NH, observed spatial distributions, and implications for the chemistry in Sgr B2. Specifically, CH2NH may be important for the formation of the recently detected species E-cyanomethanimine [1] and of the Z- and N- conformers of cyanomethanimine. Laboratory work by Balucani et al [2] indicates that reactions between the CN radical and olefins (with a carbon-carbon double bond) may proceed without a barrier, potentially making the reaction CH2NH + CN → HCNHCN viable in the interstellar medium. 1 Zaleski, D.P., et al. 2013, ApJL, 765, L10 2 Balucani, N., et al. 2000, ApJ, 545, 892

Sub-Doppler jet-cooled rovibrational spectra of ND₃H⁺, ND₂H₂⁺, and NDH₃⁺ ions in various fundamental NH modes were observed and analyzed using difference frequency generation infrared spectroscopy. The ions were generated in the concentration-modulation slit-jet expansion via a H₃⁺ proton transfer mechanism in a discharge mixture of ND₃/H₂O and H₂ gases. NH mode excitation in ND₃H⁺ ion yielded a prominent Q branch feature and parallel band rotational structure. Rotational transitions were confirmed unambiguously by four-line ground state combination differences within frequency measurement accuracy (10 MHz). The band origin was determined to be 3316.8413(9) cm⁻¹. Perturbation in the upper state was observed from analysis of residuals. In the case of ND₂H₂⁺, both NH symmetric (b-type) and anti-symmetric (c-type) modes were observed and assigned for the first time, yielding band origins of 3297.5440(1) and 3337.9050(1) cm⁻¹, respectively. The intensity for the two fundamental bands was interpreted with simple context of a bond-dipole model. The present study provided high precision ground state rotational constants (A^"=4.85675(4), B^"=3.96829(4), C^"=3.44667(6) cm⁻¹), which should facilitate microwave searches for isotope-substituted ammonium ions in the regions of interstellar medium, such as dense molecular clouds or younger stellar objects.

The CH radical is an important constituent of stellar atmospheres, interstellar gas clouds and is of fundamental importance to interstellar chemistry. Furthermore, it offers a sensitive way to test the hypothesis that fundamental constants measured on earth may differ from those observed in other parts of the universe¹. Here, we present a measurement of the lowest millimeter-wave transition of CH, near 535 GHz, with an accuracy of 0.6 kHz², an improvement of nearly two orders of magnitude compared to the previous best rest frequencies. We drive the millimeter-wave transitions using the 54th harmonic of a frequency synthesizer phase-locked to a 10 MHz GPS frequency reference. Using ALMA this transition has recently been observed in the absorber PKS 1830-211 at a redshift of z=0.89³. As pointed out by de Nijs et al.⁴ a very robust and sensitive means to search for variations in fundamental constants could be obtained by observing the lowest millimeter-wave transition of CH along with the two Λ-doublets at 3.3 and 0.7 GHz, all from the same interstellar gas cloud.
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¹S. Truppe et al., Nature Communications 4, 2600, 2013 ²S. Truppe et al., The Astrophysical Journal 780, 71, 2014 ³S. Muller, private communication, 2013 ⁴de Nijs et al., Physical Review A 86, 032501, 2012

We report the discovery for the first time in space of the nitrosylium ion, NO⁺. The observations were performed towards the cold dense core Barnard 1-b. The identification of the J = 2 ← 1 line is supported by new laboratory measurements of rotational lines of NO⁺ in the ground vibrational state up to the J = 8 ← 7 transition (953207.189 MHz). The ion was produced in a magnetically extended negative glow discharge in NO. Vibrational excitation of the ion was high enough to measure rotational lines up to v = 2. A few transitions of ¹⁵NO⁺ were also measured (v = 0, 1). All known rotational and ro-vibrational frequencies of this close-shell ion were included in an isotopically invariant analysis. In Barnard 1-b, the observed line profile of NO⁺ exhibits two velocity components at 6.5 and 7.5 km s⁻¹, with column densities of 1.5×10¹² and 6.5×10¹¹ cm⁻², respectively. New observations of NO and HNO have been performed and allowed to estimate the following abundance ratios: X(NO)/X(NO⁺) ≈ 511, and X(HNO)/X(NO⁺) ≈ 1. The chemistry of NO⁺ has been investigated by means of a time-dependent gas phase model which includes an updated chemical network according to recent experimental studies. The predicted abundance for NO⁺ and NO is found to be consistent with the observations. However, that of HNO relative to NO is too high. No satisfactory chemical paths have been found to explain the observed low abundance of HNO.

In 2012, Pety et al. (A&A, 548, A68) reported the detection of a series of transitions from 90 to 270 GHz arising from a molecular carrier (B11244) which they attributed to the l-C₃H⁺ cation, a species never-before seen in the laboratory. Theoretical work, however, suggested the anion, C₃H⁻, was a more likely carrier (Fortenberry et al. 2013, ApJ, 772, 39). We conducted several observational studies to examine these possibilities, and concluded l-C₃H⁺ was supported by the observational evidence, a conclusion which has recently been confirmed by laboratory work (Brünken et al. 2014, ApJL, 783, L4). Here, we present a body of observational results compiled in our search for l-C₃H⁺ toward more than 40 sources. Despite spanning a wide range of environments, including hot molecular cores, cold cores, PDRs, and HH objects, we find definitive evidence for l-C₃H⁺ in only three sources. We will discuss the implications of the apparent scarcity of this molecule. What is so special about these specific regions that favors the formation of this molecule, and in turn, what can l-C₃H⁺ tell us about the physical and chemical conditions within these environments? Interferometric observations with ALMA are the ideal path forward for answering these questions, and we discuss what these observations will tell us about l-C₃H⁺ and the unique environments in which it is present.

With the advent of new broadband spectral line interferometric observations, we can now begin to fully characterize the spectra and distribution of complex organic molecules that have been largely ignored since their original detections using single dish telescopes. First detected in 1973, acetaldehyde (CH₃CHO) has been detected in numerous sources including TMC-1, Sgr B2(N) and Orion KL (Gottlieb et al 1973; Mathews et al. 1984; Johansson et al. 1991); yet its distribution within these sources is still not well known. Unlike a number of other molecules observed in these regions, acetaldehyde is not observed to be concentrated in hot core regions toward Sgr B2(N), but to have an extended distribution, a trait shared by other aldehydes (Hollis et al. 2001; Chengalur and Kanekar, 2003). An extended distribution may indicate formation through gas phase ion molecule reactions, or that the distribution is a result of non-thermal processes liberating the molecule off grain surfaces. Meanwhile, a compact distribution may indicate warm grain surface chemistry with subsequent desorption by thermal processes. Spatial maps will also help determine abundance correlations with other related molecules such as formic acid, aiding in the investigation of formation routes. In this talk, we present multiple transition maps of acetaldehyde toward Orion KL using both CARMA and the ALMA Band 6 Science Verification data which show evidence of an extended distribution of acetaldehyde, suggesting a similar formation chemistry in Orion KL as suggested by Chengular and Kanekar (2003) towards Sgr B2(N). In addition, spatial correlations to other molecules in the region will be shown, possibly suggesting a common formation chemistry for some aldehydes.

An extensive search has been conducted to confirm transitions of trans-ethyl methyl ether (tEME), (C₂H₅OCH₃), toward the high mass star forming region W51 e1/e2 using the 12 m Telescope of the Arizona Radio Observatory (ARO) at 2 mm and 3 mm wavelengths. Typical peak to peak noise levels for the present observations of W51e1/e2 were between 10 mK to 30 mK, indicating an upper limit of the tEME column density of ≤ 1.5 × 10¹⁵ cm⁻², this would make tEME at least a factor 2 times less abundant than dimethyl ether (CH₃OCH₃) toward W51 e1/e2. We have also performed an extensive search for this species toward the high mass star forming region Sgr B2(N-LMH) with the NRAO 100 m Green Bank Telescope (GBT). No transitions of tEME were detected and we were able to set an upper limit to the tEME column density of ≤ 4 × 10¹⁴ cm⁻² toward Sgr B2(N-LMH). We will discuss these observations in the context of detecting large complex organic species toward star forming regions with next generation telescopes such as ALMA.

Except isocyanic acid detected in the ISM since 1972¹, the organo isocyanate derivatives are poorly studied in the millimeter wave domain. This lack of data could be the reason of their non detection in the ISM up to now. We decided to investigate the C₃H₃NO₂ isomer: acetyl isocyanate. Previously measured up to 40 GHz ², the cis-conformer exhibits internal rotation motion with a medium barrier value of 360 cm⁻¹. The trans conformer conformer is calculated to have an energy of 12.55 kJ.mol⁻¹ (1060 cm⁻¹) higher than the cis one³ and is not studied here. The measurements were performed in Lille with our solid state devices spectrometer up to 500 GHz. The sample was found to have a poor stability and reacts fastly with metal parts. We should repeat measurements using a flow and a pyrex cell in order to have satisfactory signal to noise ratio. The analysis was performed with RAM36 code⁴ which used the Rho Axis Method. The first results and its searche in ORION will be presented.
This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI. This work was also done under Ukrainian-French CNRS-PICS 6051 project and ANR-13-BS05-0008-02 IMOLABS
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¹Snyder, L. E.; and Buhl, D.Astrophys. J.  177, (1972) 619 ²Landsberg, B.M.; and Iqbal, K.J.C.S. Faraday II 76, (1980) 1208 ³Uchida, Y.; Toyoda, M.; Kuze, N.; and Sakaizumi, T.J. Mol. Spectrosc. 256, (2009) 163 ⁴Ilyushin, V.V. et al;J. Mol. Spectrosc. 259, (2010) 26

Vinyl cyanide (acrylonitrile, H₂C=CHC ≡ N) is an interstellar molecule that was classified as a 'weed' since transitions in its isotopic species and vibrationally excited states have already been detected and need to be accounted for in searches for complex organic molecules. Presently we extend the systematic analysis of the laboratory rotational spectrum of vinyl cyanide to 9 new excited vibrational states with vibrational energies above 550 cm⁻¹ (785K). The spectroscopic analysis is based on the broadband 50-1900 GHz spectrum combined from results from the participating spectroscopic laboratories and covering a total of 1235 GHz. The studied states come in the form of polyads of perturbing vibrational states, and such perturbations also affect the strong, low-K_a transitions used for astrophysical detection. It is therefore crucial to account for such effects in order to produce reliable linelists. The experimental data for three new polyads were fitted to experimental accuracy using Coriolis and Fermi perturbation models. Multiple transitions in the lowest of these polyads (and in other excited vibrational states and isotopic species of vinyl cyanide) were detected in the millimetre survey of the Orion-KL Nebula made with the IRAM 30-m radiotelescope.

We report on the detection of hydromagnesium isocyanide, HMgNC, in the laboratory and in the carbon-rich evolved star IRC+10216. The J = 1-0 and J = 2-1 lines were observed in our microwave laboratory equipment in Valladolid with a spectral accuracy of 3 kHz. The hyperfine structure produced by the nitrogen atom was resolved for both transitions. Four rotational lines of this species, J = 8-7, J = 10-9, J = 12-11, and J = 13-12, have been detected toward IRC+10216. First results for another metal bearing species are also reported.

The rotational spectrum of ethyl mercaptan, CH₃CH₂SH, has been measured in the microwave, millimeter- and submillimeter-wave regions from 8 to 880 GHz and more than 2800 distinct transition frequencies have been assigned for the gauche- and trans-conformers. Very precise values of the spectroscopic constants allowed the detection of the gauche-CH₃CH₂SH towards Orion KL.¹ 77 unblended or slightly blended lines plus no missing transitions in the range 80 - 280 GHz support this identification. Trans-CH₃CH₂SH has been detected tentatively.
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¹L. Kolesniková, B. Tercero, J. Cernicharo, A. M. Daly, J. L. Alonso, B. P. Gordon, S. Shipman, Astrophys. J. Lett. 2014, accepted.

We present a high velocity resolution (0.04 km/sec) molecular line survey of the Taurus Molecular Cloud in the frequency range 39 to 48 GHz with NSF’s Robert C. Byrd Green Bank telescope (GBT). Figure The observing method and data reduction process are outlined. We describe the method of obtaining the calibrated, averaged spectral line data online. The RMS survey sensitivity was slightly different for each 200MHz frequency band, and ranged from 0.02 to 0.15 K (T_B) for the different bands. A large number of molecular lines are detected, most of which have previously been associated with already known interstellar molecules. We present a summary processes to combine a number of lines of molecular species in order to identify new species.

Next generation interferometers offer new possibilities of extracting information about the history and conditions of interstellar regions through analysis of molecular abundance ratios, which act as chemical fingerprints. To fully utilize these new capabilities, however, complete molecular inventories of interstellar regions must be established and the relative contributions of different chemical processes must be determined. Current theories on molecule formation will therefore be guiding forces in future observing strategies. Recently, Lattelais et al. have interpreted aggregated observations of molecular isomers to suggest that there exists a “minimum energy principle”, such that molecular formation will favor more stable molecular isomers for thermodynamic reasons. To test the predictive use of this model, we have fully characterized the spectra of the three isomers of C₃H₂O toward the well known molecular region Sgr B2. Evidence for the detection of the isomers cyclopropenone (c-C₃H₂O) and propynal (HCCCHO) is presented, along with evidence for the non-detection of the lowest zero-point energy isomer, propadienone (CH₂CCO). We interpret these observations as evidence that chemical formation pathways, which may be under kinetic control, have a more pronounced effect on final isomer abundances than thermodynamic effects such as the minimum energy principle (Lattelais et al. 2009, ApJ 696, L133). These results suggest that as ALMA opens up new space for molecular discovery, focus should be placed on molecules and molecular reactions under kinetic control, and we briefly discuss the possible applications of isomeric analysis in the era of broadband interferometry.

In order to observe quantitatively organic molecules in interstellar gas, it is necessary to understand the relative importance of photonic and collisional excitations. In order to do so, collisional excitation transfer rates have to be computed. We undertook several such studies, in particular for H₂CO and HCOOCH₃. Both species are observed in many astrochemical environments, including star-forming regions. We found that those two molecules behave in their low-lying rotational levels in an opposite way. For cis methyl-formate, a non-equilibrium radiative transfer treatment of rotational lines is performed, using a new set of theoretical collisional rate coefficients. These coefficients have been computed in the temperature range 5 to 30 K by combining coupled-channel scattering calculations with a high accuracy potential energy surface for HCOOCH₃ - He. The results are compared to observations toward the Sagittarius B2(N) molecular cloud. A total of 2080 low-lying transitions of methyl formate, with upper levels below 25 K, were treated. These lines are found to probe a cold (30 K), moderately dense (n  ∼ 10⁴ cm⁻³) interstellar gas. In addition, our calculations indicate that all detected emission lines with a frequency below 30 GHz are collisionally pumped weak masers amplifying the background of Sgr B2(N). This result demonstrates the generality of the inversion mechanism for the low-lying transitions of methyl formate. For formaldehyde, we performed a similar non-equilibrium treatment, with H₂ as the collisional partner, thanks to the accurate H₂CO − H₂ potential energy surface . We found very different energy transfer rates for collisions with para-H₂ (J=0) and ortho-H₂ (J=1). The well-known absorption against the cosmological background of the 1₁₁→ 1₀₁ line is shown to depend critically on the difference of behaviour between para and ortho-H₂, for a wide range of H₂ density. ¹
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¹We thank the CNRS-PCMI French national program for continuous support and the CHESS Herschel KP program for travel supports. Discussions with C. Ceccarelli, P. Hily-Blant and S. Maret are acknowledged.