Astrochemistry has been a growing field over the past several years. As the data from the Atacama Large Millimeter Array (ALMA) becomes publicly available, new and fast techniques for the analysis of the data will need to be developed, as well as fast, sensitive laboratory techniques. This lab is in the process of building up instrumentation that will be dedicated to the measurement of astrochemically relevant species, both in the microwave and the millimeter wave regimes. Discharge experiments, laser ablation experiments, as well as time of flight measurements will be possible with this instrumentation. Coupled with instrumentation capabilities will be new software aimed at a speeding up the analysis. The laboratory data will be used to search for new molecular signatures in the interstellar medium (ISM), and help to elucidate molecular reaction pathways occurring in the ISM.

In the course of ongoing efforts to determine accurate pure rotational transition frequencies for the astronomical community, the millimeter- and submillimeter-wave spectra of HNC and selected isotopic species have been investigated using a radio-frequency discharge of (isotopically enriched) methyl cyanide. Besides the ground vibrational state, vibrational satellites from the first excited bending mode were targeted. In part, rotational transitions were observed employing the Lamb-Dip technique to obtain sub-Doppler resolution. The Lamb-dip technique has also been applied to other short-lived molecules such as carbon monosulfide, CS.

Complex molecules have been identified in star-forming regions and their formation is linked to the specific physical and chemical conditions there. They are suspected to form a role in the origins of life. Amongst these, ethanol is a fairly abundant molecule in warmer regions. For this reason, we have recently carried out laboratory measurements and analyses of the rotational spectra of the three mono-substituted deuterium isotopologues of ethanol (one of which, CH₂DCH₂OH, exists as two distinct conformers according to the position of the deuterium atom with respect to the molecular skeleton). Measurements were taken between 35-500 GHz, allowing accurate predictions in the range of radio telescopes. We have concentrated on the lowest energy anti conformers. The dataset was constrained for fitting with a standard Watson-S reduction Hamiltonian by rejecting transitions from high-lying states, which appear to be perturbed by the gauche states, and by averaging some small methyl torsional splits. This treatment is compatible with the needs for a first search in the interstellar medium, in particular in spectra taken by ALMA. For this purpose an appropriate set of predictions will be included on the Cologne Database for Molecular Spectroscopy. Previous results on the two mono-substituted ¹³C isotopologuesBouchez et al, JQSRT 113 (11), pp. 1148-1154, 2012.hich led to a tentative detection in Sgr B2(N)Belloche et al. A&A 559, id.A47, 187pp., 2013.ill be briefly summarized and compared with the latest measurements. The usefulness of studying different isotopologues in the interstellar medium will also be rapidly addressed.

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Bouchez et al, JQSRT 113 (11), pp. 1148-1154, 2012.w Belloche et al. A&A 559, id.A47, 187pp., 2013.w

Methylene, the parent of the carbene compounds, plays a crucial role in many chemical reactions. This bi-radical is a known interstellar molecule that has been detected towards hot cores in dense interstellar clouds. CH₂ is also thought to be present in cometary atmospheres. In the gas phase chemical models of both dense and diffuse molecular clouds, CH₂ is a key intermediate in interstellar carbon chemistry which is produced primarily by dissociative recombination of the methyl ion, CH⁺₃. Recently tentative detection of the mono-deuterated methyl ion, CH₂D⁺ has been reported toward an infrared source in the vicinity of Orion.D. C. Lis, P. F. Goldsmith, E. A. Bergin et al. 2009, in Submillimeter Astrophysics and Technology, ASP Conf. Ser., 417, 23.euterated methylene CHD and CD₂ can be produced from this ion or its counterpart CHD⁺₂ by dissociative recombination with an electron:

CH2D+ + e− → CHD+ H  or CH2 + D,

(\theequation)

CHD2+   + e− → CHD+ D  or CD2 + H.

(\theequation)

Thus, both CHD and CD₂ can be observed in warm interstellar clouds, where the deuterium fractionation process is important. Precise laboratory reference data are desirable for radioastronomical observation of these molecules. Here we report on our high-resolution spectroscopic investigation on the deuterated methylene radical, CD₂ (X ³B₁) up to 1.45 THz. At present time, eleven out of the twelve fine-structure components of four pure rotational transitions have been newly recorded, and these measurements double the number of previously observed transitions.H. Ozeki and S. Saito J. Chem. Phys. 1996, 104, 2167.D₂ was generated in a discharge in CD₂CO which was obtained from the flash pyrolysis of acetic anhydride-d6 ((CD₃CO)₂O). Effort is currently made to measure the astronomically important 1₁₁ − 0₀₀ transition whose fine-structure components are predicted to occur at 1.224,1.228 and 1.234 THz.

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D. C. Lis, P. F. Goldsmith, E. A. Bergin et al. 2009, in Submillimeter Astrophysics and Technology, ASP Conf. Ser., 417, 23.D H. Ozeki and S. Saito J. Chem. Phys. 1996, 104, 2167.C

Pure rotational transitions of D₂H⁺ observed by high-resolution spectroscopy have been limited so far to the J = 1₁₀-1₀₁ transition at 691.7 GHz,T. Hirao and T. Amano, Ap. J.,597, L85 (2003)J=2_20-2_11 at 1.370 THz, and J=1_11-0_00 at 1.477 THz.K. M. Evenson et al cited by O. L. Polyansky and A. R. W. McKellar, J. Chem. Phys., 92, 4039 (1990)O. Asvany et al, Phys. Rev. Lett., 100, 233004 (2008) As this ion is a light asymmetric−top molecule, spectroscopic characterization and prediction of other rotational transition frequencies are not straightforward. In this presentation, we extended the measurements up to 2 THz by using the JPL frequency multiplier chains, and observed three new THz lines and re−measured the three known transitions.D_2H^+ K. M. Evenson et al cited by O. L. Polyansky and A. R. W. McKellar, J. Chem. Phys., 92, 4039 (1990)Footnotes:

In 1937, DunhamT. Dunham, Publ. Astron. Soc. Pac., 49, 26 (1937)etected a couple of unidentified lines in near-UV, and later Douglas and HerzbergA. E. Douglas and G. Herzberg, Ap. J. 94, 381 (1941)dentified them based on their laboratory observations to be low-J electronic transitions of CH⁺. The electronic spectra, in particular the A¹Π−X¹Σ⁺ band, have been investigated extensively. On the other hand, the pure rotational transitions have not been studied so extensively. Only the lowest rotational transition, J=1−0, was observed in the laboratory for the normal species, ¹³CH⁺, and CD⁺.T. Amano, Ap.J.Lett., 716, L1 (2010)T. Amano, J. Chem. Phys., 133, 244305 (2010) Based on the laboratory frequency, CH⁺ was detected in star forming regions with the Hershel space observatory. Cernicharo et al identified pure rotational transitions from J=2−1 to J=6−5 in the far-infrared region in the ISO spectrum of the planetary nebula NGC 7027J. Cernicharo et al., Ap. J. Lett., 483, L65 (1997) The ISO spectra, however, were of low-resolution, so high-resolution spectroscopic observation is highly desirable. In this presentation, we have extended the measurements to higher-J lines up to 2 THz. For production of CH⁺, an extended negative glow discharge in a gas mixture of CH₄ ( ∼ 0.5 mTorr) diluted in He ( ∼ 60 mTorr) was used. The optimum discharge current was about 15 mA and the axial magnetic filed to 160 Gauss was applied up. The discharge cell was cooled down to liquid nitrogen temperature. Several frequency multiplier chains, developed at JPL and purchased from Virginia Diodes, were used as THz radiation sources. New THz measurements are not only useful for providing better characterization of spectroscopic properties but also will serve as starting point for astronomical observations.

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T. Dunham, Publ. Astron. Soc. Pac., 49, 26 (1937)d A. E. Douglas and G. Herzberg, Ap. J. 94, 381 (1941)i T. Amano, Ap.J.Lett., 716, L1 (2010)

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J. Cernicharo et al., Ap. J. Lett., 483, L65 (1997).

Terahertz absorption spectroscopy was employed to extend the measurements on the pure rotational transitions of N₂H⁺, N₂D⁺ and their ¹⁵N-containing isotopologues in the ground state and first excited vibrational states for the three fundamental vibrational modes. In total 88 new pure rotational transitions were observed in the range of 0.7-2.0 THz. The observed transition frequencies were fit to experimental accuracy, and the improved molecular parameters were obtained. The new measurements and predictions will support the analysis of high-resolution astronomical observations made with facilities such as SOFIA and ALMA where laboratory rest frequencies with uncertainties of 1 MHz or smaller are required for proper analysis of velocity resolved astrophysical components.

HCl⁺ is a key intermediate in the interstellar chemistry of chlorine. It has been recently identified in space from Herschel's spectraM. De Luca et al., Astrophys. J. Lett. 751, L37 (2012)nd it has also been detected in the laboratory through its optical emissionW. D. Sheasley and C. W. Mathews, J. Mol. Spectrosc. 47, 420 (1973) infraredP. B. Davies, P. A. Hamilton, B. A. Johnson, Mol. Phys. 57, 217 (1986) nd mm-wave spectraH. Gupta, B. J. Drouin, and J. C. Pearson, Astrophys. J. Lett. 751, L37 (2012) Now that Hershchel is decomissioned, further astrophysical studies on this radical ion will likely rely on ground-based observations in the mid-infrared. We have used a difference frequency laser spectrometer coupled to a hollow cathode discharge to measure the absorption spectrum of H³⁵Cl⁺ and H³⁷Cl⁺ in the v=0−1 band of the ²Π state with Dopppler limited resolution. The accuracy of the individual measurements ( ∼  10 MHz (3σ)) relies on a solid state wavemeter referenced to an iodine-stabilized Ar⁺ laser. The new data are being fit using the CALPGM software from JPL, and the current status will be presented.

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M. De Luca et al., Astrophys. J. Lett. 751, L37 (2012)a W. D. Sheasley and C. W. Mathews, J. Mol. Spectrosc. 47, 420 (1973), P. B. Davies, P. A. Hamilton, B. A. Johnson, Mol. Phys. 57, 217 (1986) a H. Gupta, B. J. Drouin, and J. C. Pearson, Astrophys. J. Lett. 751, L37 (2012) .

In our ongoing experiments on the DESIRS beam-line at the SOLEIL Synchrotron, we are acquiring the necessary data on oscillator strengths and predissociation rates for modeling CO photochemistry in astronomical environments. A VUV Fourier Transform Spectrometer with a resolving power of about 350,000 allows us to discern individual lines in electronic transitions. Here we focus on results obtained from absorption spectra of ¹³C¹⁸O, for the W ¹Π − X ¹Σ⁺ bands with v^′=0, 2, and 3 and v^′′=0 and three resolved bands involving transitions to the upper levels 4pπ(2), 5pπ(0), and 5pσ(0) of the 4p(2) and 5p(0) complexes. We compare our results with earlier determinations for this isotopologue of CO, as well as with our SOLEIL measurements on ¹²C¹⁶O, ¹³C¹⁶O, and ¹²C¹⁸O.

We present results from calculations of the physical conditions necessary for the occurrence of 36.169 (4₋₁−3₀ E), 44.070 (7₀−6₁ A⁺), 84.521 (5₋₁−4₀ E), and 95.169 (8₀−7₁ A⁺) GHz methanol (CH₃OH) maser emission lines near supernova remnants (SNRs), using the MOLPOP-CEP program. The calculations show that given a sufficient methanol abundance, methanol maser emission arises over a wide range of densities and temperatures, with optimal conditions at n ∼ 10⁴−10⁶ cm⁻³ and T > 60 K. The 36 GHz and 44 GHz transitions display more significant maser optical depths compared to the 84 GHz and 95 GHz transitions over the majority of physical conditions. It is also shown that line ratios are an important and applicable probe of the gas conditions. The line ratio changes are largely a result of the E-type transitions becoming quenched faster at increasing densities. The modeling results will be discussed using recent observations of CH₃OH masers near the SNRs G1.4−0.1, W28, and Sgr A East and used as a diagnostic tool to estimate densities and temperatures of the regions in which the CH₃OH masers are observed.

Disilicon carbide Si₂C is one of the most fascinating small molecules for both fundamental and applied reasons. Like C₃, it has a shallow bending angle, and may therefore also serve as a classic example of a quasilinear species. Si₂C is also thought to be quite stable. Mass spectrometric studies conclude that it is one of the most common gas-phase fragments in the evaporation of silicon carbide at high temperature. For these same reasons, it may be abundant in certain evolved carbon stars such as IRC+12016. Its electronic spectrum was recently studied by several of us, but its ground state geometry and rotational spectrum remain unknown until now. Using sensitive microwave techniques and high-level coupled cluster calculations, Si₂C has been detected in the radio band, and is found to be highly abundant. Its more common rare isotopic species have also be observed either in natural abundance or using isotopically-enriched samples, from which a highly precise semi-experimental structure has been derived. This talk will summarize recent work, and discuss the prospects for astronomical detection. Now that all four of the Si_mC_n clusters with m+n=3 has been detected experimentally, a rigorous comparison of their structure and chemical bonding can be made.