The CH⁺ ion was one of the first molecules identified in the interstellar gas more than 75 years ago, but the high observed abundances of CH⁺ remain a puzzle, because the main reaction proposed for the formation of CH⁺, viz., C⁺ + H₂ → CH⁺ + H, is so endothermic (4640 K), that it is unlikely to proceed at the typical temperatures of molecular clouds. One way in which the high endothermicity may be overcome, is if a significant fraction of the H₂ is vibrationally excited, as is the case in dense molecular gas exposed to intense far-ultraviolet radiation fields. Elucidating the formation of CH⁺ in molecular clouds requires characterization of its spatial distribution, as well as that of the key reactants in the chemical pathways yielding CH⁺. Here we present high-resolution spectral maps of the two lowest rotational transitions of CH⁺ and the fine structure transition of C⁺ in a  ∼ 3^′ ×3^′ region around the Orion Kleinmann-Low (KL) nebula, obtained with the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared (HIFI).¹ We compare these maps to those of CH⁺ and C⁺ in the Orion Bar photodissociation region (PDR), and discuss the excitation and abundance of CH⁺ toward Orion KL in the context of chemical and radiative transfer models, which have recently been successfully applied to the Orion Bar PDR.²
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¹These observations were done as part of the Herschel observations of EXtraordinary sources: the Orion and Sagittarius star-forming regions (HEXOS) Key Programme, led by E. A. Bergin at the University of Michigan, Ann Arbor, MI. ²Nagy, Z. et al. 2013, A&A 550, A96

Electronic transitions of polar linear molecules have been modeled and compared to archival high resolution spectra of the diffuse interstellar bands (DIBs) at 5797 and 6613 Å. These two bands are notable for fine structure that has most commonly been attributed to the rotational structure of electronic transitions of gas-phase molecules.¹ Most strikingly, the 5797 DIB has a sharp, narrow center peak that is characteristic of the Q branch of parallel transitions with non-zero Λ. This work is also motivated by Oka et al.'s analysis of the anomalously extended redward tails seen in certain DIBs toward Herschel 36, which are reminiscent of electronic transitions of polar linear molecules at high radiative temperatures.² The determination of rotational distributions, which includes radiative and collisional effects, is based on the model presented in the earlier work. Thus far, the most promising models are a ²Π← ²Π transition for the 5797 DIB and a ²∆← ²Π transition for the 6613 DIB, with the effects of spin-orbit coupling examined in each case. The degree of consistency of these transitions with respect to the anomalous DIBs toward Herschel 36 is also discussed.
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¹Sarre, P. J., Miles, J. R., Kerr, T. H. et al. 1995, MNRAS, 177L 41 ²Oka, T., Welty, D. E., Johnson, S. et al. 2013, ApJ, 773 42

Although molecules with a wide range of sizes exist in dense clouds (e.g. H(C ≡ C)_nC ≡ N with n = 0 − 5), molecules identified in diffuse clouds are all small ones. Since the initial discovery of CH, CN, and CH⁺, all molecules detected in the optical region are diatomics except for H₃⁺ in the infrared and C₃ in the visible. Radio observations have been limited up to triatomic molecules except for H₂CO and the ubiquitous C₃H₂.¹ The column densities of all molecules are less than 10¹⁴ cm⁻² with the two exceptions of CO and H₃⁺ as well as CH and C₂ in a few special sightlines. Larger molecules with many carbon atoms have been searched for but have not been detected. On the other hand, the observations of a great many diffuse interstellar bands (380 toward HD 204827² and 414 toward HD 183143³) with equivalent widths from 1 to 5700 mÅ  indicate high column densities of many heavy molecules. If an electronic transition dipole moment of 1 Debye is assumed, the observed equivalent widths translate to column densities from 5 × 10¹¹ cm⁻² to 3 × 10¹⁵ cm⁻². It seems impossible that these large molecules are formed from chemical reactions in space from small molecules. It is more likely that they are fragments of aggregates, perhaps mixed aromatic/aliphatic organic nanoparticles (MAONS).⁴ MAONS and their large fragment molecules are stable against photodissociation in the diffuse ISM because the energy of absorbed photons is divided into statistical distributions of vibrational energy and emitted in the infrared rather than breaking a chemical bond. We use a simple Rice-Ramsperger-Kassel-Marcus theory⁵ to estimate the molecular size required for the stabilization.
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¹Snow, T. P. & McCall, B. J. 2006, ARA&A, 44 367 ²Hobbs, L. M., York, D. G., Snow, T. P., Oka, T., Thorburn, J. A., et al. 2008, ApJ, 680 1256 ³Hobbs, L. M., York, D. G., Thorburn, J. A., Snow, T. P., Bishof, M., et al. 2009, ApJ, 705 32 ⁴Kwok, S. & Zhang, S. 2013, ApJ, 771 5 ⁵Freed, K. F., Oka, T., & Suzuki, H. 1982, ApJ, 263 718

Since last year, infrared spectra of H₃⁺ and CO have been obtained toward nine stars (designated by us α+, β, γ, γ−, δ, θ, κ, λ, and λ−) along the Galactic plane from 138 pc to the west of Sgr A* to 115 pc east, using IRCS of the Subaru Telescope and GNIRS of the Gemini North Observatory. All of the objects lie within the Central Molecular Zone (CMZ), a region of radius  ∼ 150 pc at the center of the Galaxy. All sightlines except that toward λ (a red giant not suitable for H₃⁺ spectroscopy) have high H₃⁺ column densities on the order of a few times 10¹⁵ cm⁻². The metastable R(3,3)^l absorption line was sought on seven sightlines (α+, β, γ, γ−, δ, θ, κ), each of which showed significant signal except κ for which detection of this line was inconclusive. These results indicate that the long (at least several tens of parsecs) columns of warm (T  ∼  250 K) and diffuse (n  ≤  100 cm⁻³) gas in which a high ionization rate of ζ of a few times 10⁻¹⁵ s⁻¹ exists, found earlier by us on sightlines passing through the central 30 pc of the CMZ¹² are present over nearly the entire CMZ. The velocity profiles of the H₃⁺ absorption lines provide information on the morphology of the diffuse gas in the CMZ. The velocity profile toward star λ− (2MASS J17482472-2824313) observed by GNIRS is particularly noteworthy. The sightline toward this star, located 115 pc to the east of Sgr A*, shows the presence of warm diffuse gas near 0 radial velocity and complements an identical result at the west end (on sightlines toward α+ and previously observed sources α and β). Stars nearer to the center of the CMZ show the warm diffuse gas at negative velocities only. Although many more stars need to be observed, the results to date suggest the existence of an expanding molecular ring of diffuse gas which is, unlike previously reported, not rotating but purely expanding.³
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¹Oka, T., Geballe, T. R., Goto, M., Usuda, T., and McCall, B. J. 2005, ApJ, 632 882 ²Goto, M., Usuda, T., Nagata, T. et al. 2008, ApJ, 688 306 ³Oka, T. 2013, Chem. Rev. 113 8738

From observed high H₃⁺ column densities in the Central Molecular Zone (CMZ), a region with a radius of  ∼ 150 pc at the center of our Milky Way Galaxy, H₂ ionization rates of ζ  ∼  3 × 10⁻¹⁵ s⁻¹ have been reported.¹² This ionization rate which is higher than those in dense clouds and diffuse clouds in the Galactic disk by  ∼ 100 and  ∼ 10, respectively, have been ascribed to high flux of cosmic rays due to the high density of supernova remnants in the region. We are studying the ionization rate due to X-rays intensely observed in the CMZ as a possible competing process. Last year we reported the estimated ionization rate due to observable X-rays with energy 1 - 10 keV as negligible compared to the observed ζ. However, just like cosmic ray ionization is dominated by low energy (E ≤  100 MeV) cosmic rays that are not directly observable because of deflection by solar magnetic field, the X-ray ionization is dominated by soft X-rays (E ≤  1 keV) that are not observable due to optical depth of the foreground gas. Our task therefore resembles those by Hayakawa et al. (1961)³ and Spitzer and Tomasko (1968)⁴ who estimated the cosmic ray ionization rate ζ based on high energy ( >  1 GeV) cosmic ray observations. We use theoretical X-ray spectrum and interpolate the observed X-rays at 4 keV, which are observable nearly un-attenuated from the CMZ, to the low energy region. Two theoretical spectra are presented, one due to Bremsstrahlung with variable temperature and proper cut off and the other the advection-dominated accretion flow (ADAF) model.⁵. Discussion of the calculations and the results will be presented.
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¹Oka, T., Geballe, T. R., Goto, M., Usuda, T., and McCall, B. J. 2005, ApJ, 632 882 ²Geballe, T. R., and Oka, T. 2010, ApJ, 709 L70. ³Hayakawa,S.,Nishimura, S., Takayanagi, K. 1961, PASJ, 18 184 ⁴Spitzer,L. T., Tomasko, M. G. 1968, ApJ, 152 971 ⁵Yuan, F., Quataert, E., Narayan, R. 2003, JPJ, 598 301.

Near the Galactic center, the presence of the supermassive black hole, high dust temperatures, and large densities produce an unique environment within our galaxy. Unfortunately, optical light in this region is obscured by dust, making optical observations difficult or impossible. By utilizing radio telescopes, we can peer through the dust to examine the inner workings of this fascinating region. Using the Very Large Array, we examined the Galactic center radio source N3, a point source located within the Radio Arc. Our observations examined both molecular line and continuum emission from the region at frequencies from 2 GHz to 49 GHz. Several molecular species are detected around N3. Using molecular line analysis, N3's spectral index, physical size limits, and possible interactions between N3 and the Radio Arc, we examine the physical nature of N3 and outline further work needed to complete the analysis of this interesting source.

Observations were made of a number of carbon-rich circumstellar envelopes using the Phoenix spectrograph on the Gemini South telescope to determine the presence of small carbon chain molecules. The circumstellar envelope of IRC+10216 (CRL 1381) has been extensively studied, due to its brightness in the infrared, and C₃ and C₅ have previously been observed¹². Vibration-rotation lines of the ν₃ antisymmetric stretch of C₃ near 2040 cm⁻¹have been used to determine the column density of C₃ in three new circumstellar envelopes: CRL 865, CRL 1922 and CRL 2023. Our new observations support the column density determined from CRL 1381 and also demonstrate that C₃ is common in carbon-rich circumstellar shells. We additionally determine upper limits for the small carbon chains, C₅ and C₇.
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¹Hinkle, K.W., Keady, J.J., & Bernath, P.F. 1988, Science, 241, 1319 ²Bernath, P.F., Hinkle, K.H., & Keady, J.J. 1989, Science, 244, 562

By observing the astronomical masers in the Milky Way we can determine for instance high-accurate distances of the hosting Galactic sources (e.g., Galactic star-forming regions) and the kinematic of the gas where the masers arise (e.g., the kinematic of Keplerian accretion disks and outflows in massive star-forming regions). In addition, the bright and narrow spectral line emissions of water and methanol masers are ideal for measuring the Zeeman splitting as well as for determining the orientation of the magnetic field in 3-dimensions around massive young stellar objects (YSOs). Therefore, water and methanol maser species can help us to answer several crucial questions about massive star-formation. For instance, one of the most debated question is whether magnetic fields are important in the formation of high-mass stars (M > 8 M_sun). The main difficulty in answering this question is related to the fast evolution of the high-mass stars that makes the massive YSOs rare. Furthermore, they are typically found at fairly large distance. Hence, it is very difficult to measure the magnetic fields at distances < 100 Astronomical Units from the central protostar by using dust polarized emissions. But fortunately, the direct measurement of magnetic fields at small scale (10-100 Astronomical Units) around massive YSOs is possible by observing the polarized emission of masers.
In my oral contribution, besides showing the polarization properties of 22-GHz water and 6.7-GHz methanol masers, I will show our most interesting results about the determination of the orientation and of the strength of magnetic fields around massive YSOs. We have also started a systematic study for determining if there exists a real alignment between magnetic fields and the large scale outflows that are launched from the central protostar, which is important to constrain future simulations. Furthermore, we are involved in laboratory and modelling efforts to calibrate the magnitude of the Zeeman effect for methanol masers.

Interstellar matter is not inert, but is constantly evolving. On the one hand, its physical characteristics such as its density and its temperature, and on the other hand, its chemical characteristics such as the abundances of the species and their distribution, can change drastically. The phases of this evolution spread over different timescales, and this matter evolves to create very different objects such as molecular clouds (T  ∼ 10 K, n  ∼ 10⁴ cm⁻³, t  ∼ 10⁶ years), collapsing prestellar cores (inner core : T  ∼ 1000 K, n  ∼ 10¹⁶ cm⁻³, t  ∼ 10⁴ years), protostellar cores (inner core : T  ∼ 10⁵ K, n  ∼ 10²⁴ cm⁻³, t  ∼ 10⁶ years), or protoplanetary disks (T  ∼ 10−1000 K, n  ∼ 10⁹−10¹² cm⁻³, t  ∼ 10⁷ years). These objects are the stages of the star formation process. Starting from the diffuse cloud, matter evolves to form molecular clouds. Then, matter can condense to form prestellar cores, which can collapse to form a protostar surrounded by a protoplanetary disk. The protostar can evolve in a star, and planets and comets can be formed in the disk. Thus, modeling of astrochemistry during star formation should consider chemical and physical evolution in parallel. We present a new gas-grain chemical network involving deuterated species, which takes into account ortho, para, and meta states of H₂, D₂, H₃⁺, H₂D⁺, D₂H⁺, and D₃⁺. It includes high temperature gas phase reactions, and some ternary reactions for high density, so that it should be able to simulate media with temperature equal to [10;800] K and density equal to [ ∼ 10⁴; ∼ 10¹²] cm⁻³. We apply this network to the modeling of low-mass and high-mass star formation, using a gas-grain chemical code coupled to a time dependent physical structure. Comparisons with observational constraints, such as the HDO/H₂O ratio in high mass star forming region, give good agreement which is promising. Besides, high density conditions have highlighted some limitations of our grain surface modeling. We present a numerical technique to model in a more realistic way H₂ diffusion and desorption in high density conditions.

We are conducting experiments on the DESIRS beam-line at the SOLEIL Synchrotron to acquire the necessary data on oscillator strengths and predissociation rates for modeling CO photochemistry in astronomical environments. A VUV Fourier Transform Spectrometer provides a resolving power of about 350,000, allowing us to discern individual lines in electronic transitions. Here we focus on results obtained from absorption spectra of ¹³C¹⁶O and ¹²C¹⁸O for the W ¹Π − X ¹Σ⁺ bands with v^′=0−3 and v^′′=0 and the four overlapping bands (three resolved and one diffuse) observed between 92.97 and 93.35 nm. The three resolved bands are transitions to the upper levels 4pπ(2), 5pπ(0), and 5pσ(0) of the 4p(2) and 5p(0) complexes, and the diffuse band is associated with a non Rydberg level I ¹Π; weak features in ¹³C¹⁶O are likely associated with absorption to the 4pσ(2) and II ¹Π levels. Several perturbations are also revealed in the high-resolution spectra. We compare our results with earlier determinations for these isotopologues of CO, as well as our SOLEIL measurements on ¹²C¹⁶O.

As part of a series of new photoabsorption measurements of CO isotopologues in the vacuum-ultraviolet at the SOLEIL synchrotron, we have studied the v=1 level of the W ¹Π Rydberg state. This state is crossed by an unknown perturber that strongly influences the predissociation rate of W ¹Π rotational levels. A detailed multi-isotopologue study of this interaction reveals the molecular constants of the interacting species and gives clues to its identity. Our measurement program has astrophysical applications in mind, with CO photodissociation being a critical step in the photochemistry of interstellar clouds, protoplanetary disks, and (exo)planetary atmospheres. The careful analysis of perturbations such as this and other weak features in the spectrum of CO give critical information regarding the electronic structure of the molecule. Illuminating this structure will help translate laboratory measurements to astrophysically-relevant cross sections and predissociation rates, and is itself an interesting problem in molecular physics.

The linear triatomic carbon (C₃), one of the most important molecules that have been identified in both dense and diffuse interstellar environments, has attracted great interest to astronomers and astrochemists. It is also of fundamental interest as it serves as a benchmark system for quantum chemistry. In this presentation, we report the high-resolution infrared spectra of C₃ in the 3.1 μm region. The C₃ molecules are produced in a supersonic pulsed planar plasma by discharging a propyne/helium/argon gas mixture. Continuous-wave cavity ringdown spectroscopy is used to record the infrared absorption spectra of C₃. In total, eighteen vibrational bands are observed in the 3110 - 3290 cm⁻¹range, and sixteen of them are reported for the first time. It is found that, the vibrational temperatures for the two CC stretch modes of C₃ are up to 8000 K in our plasma source, allowing to experimentally determine the ro-vibrational levels of C₃ to the 10 000 cm⁻¹region. Accurate spectroscopic parameters are obtained from the detailed analysis of our spectra. The molecular data reported here are used to test the very recent theoretical work beyond the 'gold standard' ¹ for a comprehensive understanding of the ground-state potential energy surface of C₃.
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¹P. Botschiwina, private communication.

Diffuse interstellar bands (DIBs) still remain the longest standing unsolved problem in spectroscopy and astrochemistry, although several hundreds of DIBs have been already detected. It is expected that identifications of DIBs can give us crucial information for extraterrestrial organic molecule. One of the best approaches to identify carrier molecules of DIBs is a measurement of DIB candidate molecule produced in the laboratory to compare their absorption spectra with astronomically observed DIB spectra.
Radical in a gas phase is a potential DIB candidate molecule. The electronic transitions of polyaromatic hydrocarbon radicals result in optical absorption. However, because radicals are unstable, their electronic transitions are difficult to observe using a laboratory spectrometer system. To solve this difficulty, we have developed a glow-discharge cell using a hollow cathode in which radicals can be effectively produced as a high-density plasma. The radicals produced were measured by using the cavity ringdown (CRD) spectrometer and the discharge emission spectrometer.
The CRD spectrometer, which consists of a tunable pulse laser system, an optical cavity and a discharge device, is an apparatus to observe an high-resolution optical absorption spectrum. The electronic transition of the thiophenoxy radical C₆H₅OS was observed in the discharge emission of thiophenol C₆H₅OH. The electronic transition frequency of the thiophenoxy radical was measured.
A optical discharge emission was examined by using a HORIBA Jobin Yvon iHR320 monochromator. We detected the phenoxy radical C₆H₅O in the discharge of phenol C₆H₅OH. The band observed at 6107 Å in the discharge was assigned to the electronic transition of the phenoxy radical on the basis of the sample gas dependences and the reported low resolution spectrum.¹ The electronic transition frequency of the phenoxy radical was measured.
Comparison studies of the thiophenoxy and phenoxy radicals were made with known DIB spectra.
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¹B. Ward, Spectrochimica Acta, 24A, 813, 1968

For thirty years,¹ the Polycyclic Aromatic Hydrocarbons (PAHs) have been suspected to give rise to the numerous Unidentified Infrared Bands (UIBs) observed in most astrophysical objects. Pure carbon molecules as well as derivatives with nitrogen atom(s) incorporated into the carbon skeleton have been considered. These N-bearing molecules are interesting candidates for astronomical research since they possess a larger permanent dipole moment than purely carbon-based PAHs. Most of the data reported in the literature deal with rotationally unresolved data. During the last decade, high-resolution microwave spectroscopy initiated high resolution studies of this broad family of molecules.² Recent advances in laboratory techniques permitted to provide interesting new results to rotationally resolve the IR/Far-IR vibrational bands of these relatively large C-bearing molecules³,in particular, making use of synchrotron radiation as the IR continuum source of high resolution Fourier transform (FT) spectrometers. We will present an overview of the synchrotron-based high resolution FTIR spectroscopy of 5 aza-derivatives of naphthalene (isoquinoline, quinoline, quinoxaline, quinazoline, [1,5] naphthyridine) using a room temperature long path absorption cell at the French facility SOLEIL. In support to the rovibrational analysis of these FIR spectra, very accurate anharmonic DFT calculations were performed.⁴
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¹A. Leger, J. L. Puget, Astron. Astrophys. 137, L5-L8 (1984); L. J. Allamandola et al. Astrophys. J. 290, L25-L28 (1985). ²Z. Kisiel et al. J. Mol. Spectrosc. 217, 115 (2003); S. Thorwirth et al. Astrophys. J. 662, 1309 (2007); D. McNaughton et al. J. Chem. Phys. 124, 154305 (2011). ³S. Albert et al. Faraday Discuss. 150, 71-99 (2011); B. E. Brumfield et al. Phys. Chem. Lett. 3, 1985-1988 (2012); O. Pirali et al. Phys. Chem. Chem. Phys. 15, 10141 (2013). ⁴M. Goubet, O. Pirali, J. Chem. Phys., 140, 044322 (2014).

Small metal-containing molecules were produced in a laser ablation supersonic jet apparatus. The products were investigated by means of millimeter/submillimeter wave spectroscopy and optical spectra were recorded with a high-resolution grating spectrometer (HR2000+, OceanOptics).
This method has been applied to study AlO produced from laser ablation of solid aluminum seeded in helium-buffer gas enriched with 2% of nitrogenous oxide. The adiabatically expanding dilute gas mixture is probed by monochromatic radiation of frequencies up to 400 GHz (WR2.8x3,Virginia Diodes Inc.). The measurements reveal the hyperfine structure of a linear molecule in Hund’s case b_βS due to the nuclear spin of aluminum. With the present measurements, new high accurate line positions for future astronomical observations and more accurate molecular parameters are available. The new data were compared to high level ab initio calculations performed by the group of J. Gauss.