Search

THE ''LIfe in Space'' project was funded in the wake of the Italian Space Agency's proposal for the development of a network of institutions and laboratories conceived to implement Italian participation in space astrobiology experiments. Of primary concern for this project is the study of the origin of life in the Universe, a focus that will promote investigation into prebiotic chemistry in various possible scenarios, whether in polar or nonpolar solvents (e.g., Titan's environment). Such results will link with study of the effects of simulated space conditions on possible chemical bio- signatures. The limits of life as we know it will be investigated in ground-based experiments with microorganisms that have already demonstrated their resistance to extreme environments on Earth and to real or simulated space conditions. The potential survival of microorganisms will also be examined with up-to-date molecular methods. The ability of some microorganisms to produce atmospheric and surface biosignatures when exposed to simulated conditions will be tested and compared with the possible existence of bio- signatures on potentially habitable exoplanets. Furthermore, the search for potentially habitable exoplanets, with space- based observational methods, will be optimized by way of dedicated climate models with the capacity to predict the detectability of atmospheric biosignatures for a broad range of planetary conditions. The project embraces the four most important topics in astrobiological research, as listed below, along with relevant contributions from the participating Italian institutions. Origins and evolution of organic compounds of biological significance in space (comets, asteroids, rocky planets, and moons); Prebiotic syntheses, origin of life, and early life; The limits of life and biological habitability: origin, evolution and adaptation of life in extreme environments on Earth and in space; Biomarkers for life detection in the Solar System and on exoplanets.

The cyanate anion (NCO-) is a species of considerable astrophysical relevance. It is widely believed to be embedded in interstellar ices present in young stellar objects but has not yet been detected in the dense gas of the interstellar medium. Here we report highly accurate laboratory measurements of the rotational spectrum of the N13CO-isotopologue at submillimeter wavelengths along with the detection of three additional lines of the parent isotopologue up to 437.4 GHz. With this new data, the rotational spectrum of both isotopologues can be predicted to better 0.25 km s-1in equivalent radial velocity up to 1 THz, more than adequate for an astronomical search in any source. Moreover, a semiexperimental equilibrium structure of the anion is derived by combining the experimental ground-state rotational constants of the two isotopologues with theoretical vibrational corrections, obtained by using the coupled-cluster method with inclusion of single and double excitations and perturbative inclusion of triple excitations (CCSD(T)). The estimated accuracy of the two bond distances is on the order of 5 × 10-4Å: a comparison to the values obtained by geometry optimization with the CCSD(T) method and the use of a composite scheme, including additivity and basis-set extrapolation techniques, reveals that this theoretical procedure is very accurate.

International audience; Prebiotic sugars are thought to be formed on primitive Earth by the formose reaction. However, their formation is not fully understood and it is plausible that key intermediates could have formed in extraterrestrial environments and subsequently delivered on early Earth by cometary bodies. 1,2-Ethenediol, the enol form of glycolaldehyde, represents a highly reactive intermediate of the formose reaction and is likely detectable in the interstellar medium. Here, we report the identification and first characterization of (Z)-1,2-ethenediol by means of rotational spectroscopy. The title compound has been produced in the gas phase by flash vacuum pyrolysis of bis-exo-5-norbornene-2,3-diol at 750 degrees C, through a retro-Diels-Alder reaction. The spectral analysis was guided by high-level quantum-chemical calculations, which predicted spectroscopic parameters in very good agreement with the experiment. Our study provides accurate spectral data to be used for searches of (Z)-1,2-ethenediol in the interstellar space.

The conformational isomerism of isopropylamine and n-propylamine has been investigated by means of an integrated strategy combining high-level quantum-chemical calculations and high-resolution rotational spectroscopy. The equilibrium structures (and thus equilibrium rotational constants) as well as relative energies of all conformers have been computed using the so-called "cheap" composite scheme, which combines the coupled-cluster methodology with second-order Møller-Plesset perturbation theory for extrapolation to the complete basis set. Methods rooted in the density functional theory have been instead employed for computing spectroscopic parameters and for accounting for vibrational effects. Guided by quantum-chemical predictions, the rotational spectra of isopropylamine and n-propylamine have been investigated between 2 and 400 GHz with Fourier transform microwave and frequency-modulation millimeter/submillimeter spectrometers. Spectral assignments confirmed the presence of several conformers with comparable stability and pointed out possible Coriolis resonance effects between some of them.

Cyclopropanecarboxaldehyde (CPCA) has two main conformers, syn and anti, that are renowned for being very close in energy. Thestability order of these two main species is constantly reversed by changing the level of theory or the experimental technique employed in its determination. The anti conformer is predicted to be the most favoured in condensed states of matter, but uncertainty still remains on the relative stability in the gas phase. To gain further insights into this issue, the investigation of the rotational spectrum of both syn- and anti-CPCA has been extended in the 246–294 GHz frequency region and complemented by a detailed computational study of both conformers. A fit incorporating the recorded rotational transitions as well as those reported in the literature led to the accurate determination of the rotational parameters, also including high-order centrifugal distortion constants. Accurately computed vibrational frequencies were used to re-analyse the infrared spectrum of both conformers, thereby allowing a re-assignment of two vibrational bands, namely (Formula presented.) of anti-CPCA and (Formula presented.) of the syn conformer. While our state-of-the-art computations favour the anti conformer in the stability order, estimates from analysis of rotational spectra are rather controversial and are strongly affected by several factors, such as the zero-point vibrational correction.

In light of its ubiquitous presence in the interstellar gas, the chemistry and reactivity of the HCO+ ion requires special attention. The availability of up-to-date collisional data between this ion and the most abundant perturbing species in the interstellar medium is a critical resource in order to derive reliable values of its molecular abundance from astronomical observations. This work intends to provide improved scattering parameters for the HCO+ and He collisional system. We have tested the accuracy of explicitly correlated coupled-cluster methods for mapping the short- and long-range multi-dimensional potential energy surface of atom-ion systems. A validation of the methodology employed for the calculation of the potential well has been obtained from the comparison with experimentally derived bound-state spectroscopic parameters. Finally, by solving the close-coupling scattering equations, we have derived the pressure broadening and shift coefficients for the first six rotational transitions of HCO+ as well as inelastic state-to-state transition rates up to j = 5 in the 5-100 K temperature interval., 8 pages, 5 figures

The first high-resolution infrared spectra of CH2D37Cl have been investigated in the region 650–1100 cm−1 where the lowest fundamental bands ν5 (826.2626 cm−1), ν6 (708.4307 cm−1), and ν9 (986.3405 cm−1) occur. These vibrations perturb each other by different weak interactions and the v5 = 1 and v6 = 1 states were treated according to a model which accounts for a c-type Coriolis resonance. The spectral analysis resulted in the identification of 1664, 2550 and 2657 ro-vibrational transitions for ν5, ν6, and ν9 bands respectively, and to the determination of accurate spectroscopic parameters by using the Watson’s A-reduction Hamiltonian in the Ir representation. The simulations of the ro-vibrational structure of the ν5, ν6, and ν9 bands performed in different spectral regions adequately reproduce the experimental data.

Cyanoacetylene, the simplest cyanopolyyne, is an abundant interstellar molecule commonly observed in a vast variety of astronomical sources. Despite its importance as a potential tracer of the evolution of star-forming processes, the deuterated form of cyanoacetylene is less observed and less studied in the laboratory than the main isotopologue. Here, we report the most extensive spectroscopic characterization of DC$_3$N to date, from the millimeter domain to the infrared region. Rotational and ro-vibrational spectra have been recorded using millimeter-wave frequency-modulation and Fourier-transform infrared spectrometers, respectively. All the vibrational states with energy up to 1015 cm$^{-1}$ have been analyzed in a combined fit, where the effects due to anharmonic resonances have been adequately accounted for. The analysis contains over 6500 distinct transition frequencies, from which all the vibrational energies have been determined with good precision for many fundamental, overtone, and combination states. This work provides a comprehensive line catalog for astronomical observations of DC$_3$N, 14 pages, 3 figures, 8 tables, accepted for publication in JQSRT

Aminoacetonitrile, a molecule detected in the interstellar medium only towards the star-forming region Sagittarius B2 (Sgr B2) thus far, is considered an important prebiotic species. To date, observations were limited to ground state emission lines, whereas transitions from within vibrationally excited states remained undetected. We wanted to accurately determine the energies of the low-lying vibrational states of aminoacetonitrile, which are expected to be populated in Sgr B2(N1), the main hot core of Sgr B2(N). This step is fundamental in order to properly evaluate the vibration-rotation partition function of aminoacetonitrile as well as the line strengths of the rotational transitions of its vibrationally excited states. This is necessary to derive accurate column densities and secure the identification of these transitions in astronomical spectra. The far-infrared ro-vibrational spectrum of aminoacetonitrile has been recorded in absorption against a synchrotron source of continuum emission. Three bands, corresponding to the lowest vibrational modes of aminoacetonitrile, were observed in the frequency region below 500 cm$^{-1}$. The combined analysis of ro-vibrational and pure rotational data allowed us to prepare new spectral line catalogs for all the states under investigation. We used the imaging spectral line survey ReMoCA performed with ALMA to search for vibrationally excited aminoacetonitrile toward Sgr B2(N1). On the basis of these spectroscopic predictions, we report the interstellar detection of aminoacetonitrile in its $v_{11}=1$ and $v_{18}=1$ vibrational states toward Sgr B2(N1) in addition to emission in its vibrational ground state. The intensities of the identified $v_{11}=1$ and $v_{18}=1$ lines are consistent with the detected $v=0$ lines under LTE at a temperature of 200 K for an aminoacetonitrile column density of $1.1 \times 10^{17}$ cm$^{-2}$., 14 pages, 7 figures, 5 tables, accepted for publication in A&A

In the present work we carried out a combined rotational and ro-vibrational investigation on 1,1,2-trifluoroethene, a relevant unsaturated hydrofluoroolefin recently proposed as refrigerant in mixture with other halogenated compounds (like difluoromethane). By employing a frequency-modulation millimeter-wave spectrometer, the rotational spectra were recorded in the frequency ranges 80–96 GHz and 245–260 GHz for the ground and also the vibrationally excited states ν 8 = 1 , ν 9 = 1 , ν 12 = 1 , ν 9 = 2 , ν 12 = 2 , and ν 9 = ν 12 = 1 . In addition, the infrared spectra in the region of the ν6 band (centered at 929.8 cm − 1 ) were measured with a high-resolution Fourier transform spectrometer. The data coming from the detailed rotational and ro-vibrational assignments were combined in a global fit, taking into account also the ground state transitions available in the literature. From this analysis, a very accurate set of rotational and centrifugal distortion constants was determined for the ground state and for all the vibrationally excited states here investigated.

Phenylmethanimine is an aromatic imine with a twofold relevance in chemistry: organic synthesis and astrochemistry. To tackle both aspects, a multidisciplinary strategy has been exploited and a new, easily accessible synthetic approach to generate stable imine‐intermediates in the gas phase and in solution has been introduced. The combination of this formation pathway, based on the thermal decomposition of hydrobenzamide, with a state‐of‐the‐art computational characterization of phenylmethanimine laid the foundation for its first laboratory observation by means of rotational electric resonance spectroscopy. Both E and Z isomers have been accurately characterized, thus providing a reliable basis to guide future astronomical observations. A further characterization has been carried out by nuclear magnetic resonance spectroscopy, showing the feasibility of this synthetic approach in solution. The temperature dependence as well as possible mechanisms of the thermolysis process have been examined., A multidisciplinary approach involving organic synthesis and high‐resolution molecular spectroscopy has led to the definition of a thermally tunable formation route for imines. Its application to phenylmethanimine combined with an integrated rotational spectroscopy–quantum chemistry protocol has enabled the full characterization of the latter, thus providing the means for future astronomical observations.

In the context of radio-astronomical observations, laboratory experiments constitute a cornerstone in the interpretation of rich line surveys due to the concomitant presence of numerous emitting molecules. Here, we report the investigation of three different rotational transitions of mono-deuterated ammonia (NH2D), a species of astrophysical interest, for which the contribution of the deuterium nuclear spin to the rotational spectrum has been resolved for the first time in the millimeter- and submillimeter-wave domain. The effect of hyperfine interactions on the rotational spectrum has been unveiled by a combined theoretical and experimental approach. Quantum-chemical calculations based on coupled-cluster theory have been employed to evaluate the hyperfine parameters of nitrogen, hydrogen, and deuterium in NH2D. Subsequently, the Lamb-dip technique has been used to investigate the rotational spectrum of NH2D at high-resolution. In detail, three low-J transitions have been recorded at 86, 110, and 333 GHz with a frequency-modulation millimeter-/submillimeter-wave spectrometer. From the line profile analysis of the recorded spectra, the main terms responsible for the rotational hyperfine structure have been determined with good accuracy. Our work allows a comprehensive analysis of the rotational features of NH2D in radioastronomical spectra and a more accurate evaluation of its column density, especially in non-turbulent regions showing narrow linewidths.

We present the study of deuteration of cyanoacetylene (HC$_3$N) towards a sample of 28 high-mass star-forming cores divided into different evolutionary stages, from starless to evolved protostellar cores. We report for the first time the detection of DC$_3$N towards 15 high-mass cores. The abundance ratios of DC$_3$N with respect HC$_3$N range in the interval 0.003$-$0.022, lower than those found in low-mas protostars and dark clouds. No significant trend with the evolutionary stage, or with the kinetic temperature of the region, has been found. We compare the level of deuteration of HC$_3$N with those of other molecules towards the same sample, finding weak correlation with species formed only or predominantly in gas phase (N$_2$H$^+$ and HNC, respectively), and no correlation with species formed only or predominantly on dust grains (CH$_3$OH and NH$_3$, respectively). We also present a single-dish map of DC$_3$N towards the protocluster IRAS 05358+3543, which shows that DC$_3$N traces an extended envelope ($\sim$0.37 pc) and peaks towards two cold condensations separated from the positions of the protostars and the dust continuum. The observations presented in this work suggest that deuteration of HC$_3$N is produced in the gas of the cold outer parts of massive star-forming clumps, giving us an estimate of the deuteration factor prior to the formation of denser gas., Comment: Accepted in Monthly Notices of the Royal Astronomical Society -- 11 pages, 7 Figures, 2 Tables. Version with some typos corrected

The rotational spectrum of the most stable conformer of ethylene glycol (HO(CH$_2$)$_2$OH) has been recorded between 360-890 GHz using a frequency-modulation sub-millimeter spectrometer. The refinement and extension of the spectroscopic parameters over previous efforts provides predicted catalog frequencies for ethylene glycol with sufficient accuracy for comparison to high-frequency astronomical data. The improvement in the cataloged line positions, and the need for improved accuracy enabled by high-frequency laboratory work, is demonstrated by an analysis of ethylene glycol emission at 890 GHz in the high-mass star-forming region NGC 6334I in ALMA Band 10 observations. The need for accurate rotational spectra at sub-millimeter wavelengths/THz frequencies is discussed., accepted in the Journal of Physical Chemistry A

Chloromethane is the only organochloride detected in space to date. Its recent observation towards the low-mass protostar IRAS 16293-2422 with ALMA offers a prompt for new laboratory studies of CH$_3$Cl and its isotopologues. Here, we report the investigation of the rotational spectrum of monodeuterated chloromethane CH$_2$DCl in the frequency region between 90 and 300 GHz. The measurements have been carried out with a frequency-modulation millimeter-wave spectrometer, arranged to perform saturation spectroscopy. From the analysis of hyperfine-resolved spectra of the two chlorine isotopologues CH$_2$D$^{35}$Cl and CH$_2$D$^{37}$Cl, consistent sets of accurate spectroscopic parameters have been obtained. This work provides reliable spectral predictions which can be used to guide radio-astronomical searches of CH$_2$DCl in the interstellar medium and represents a solid base for future analyses of high-resolution infrared spectra of monodeuterated chloromethane., 13 pages, 2 figures, 3 tables

Quantifying molecular abundances of astrochemical species is a key step towards the understanding of the chemistry occurring in the interstellar medium. This process requires a profound knowledge of the molecular energy levels, including their structure resulting from weak interactions between nuclear spins and the molecular rotation. With the aim of increasing the quality of spectral line catalogs for the singly- and doubly-deuterated ammonia (NH2D and ND2H), we have revised their rotational spectra by observing many hyperfine-resolved lines and more accurate high-frequency transitions. The measurements have been performed in the submillimeter-wave region (265–1565 GHz) using a frequency modulation submillimeter spectrometer and in the far-infrared domain (45–220 cm−1) with a synchrotron-based Fourier-transform interferometer. The analysis of the new data, with the interpretation of the hyperfine structure supported by state-of-the-art quantum-chemical calculations, led to an overall improvement of all spectroscopic parameters. Moreover, the effect of the inclusion of deuterium splittings in the analysis of astrophysical NH2D emissions at millimeter wavelengths has been tested using recent observations of the starless core L1544, an ideal astrophysical laboratory for the study of deuterated species. Our results show that accounting for hyperfine interactions leads to a small but significant change in the physical parameters used to model NH2D line emissions.

Context. Deuterium fractionation processes in the interstellar medium (ISM) have been shown to be highly efficient in the family of nitrogen hydrides. To date, observations have been limited to ammonia (NH2D, NHD2, ND3) and imidogen radical (ND) isotopologues. Aims. We want to explore the high-frequency windows offered by the Herschel Space Observatory to search for deuterated forms of the amidogen radical NH2 and to compare the observations against the predictions of our comprehensive gas-grain chemical model. Methods. Making use of the new molecular spectroscopy data recently obtained at high frequencies for NHD and ND2, we searched for both isotopologues in the spectral survey toward the Class 0 protostar IRAS 16293-2422, a source in which NH3, NH, and their deuterated variants have previously been detected. We used the observations carried out with HIFI (Heterodyne Instrument for the Far-Infrared) in the framework of the key program “Chemical Herschel surveys of star forming regions” (CHESS). Results. We report the first detection of interstellar NHD and ND2. Both species are observed in absorption against the continuum of the protostar. From the analysis of their hyperfine structure, accurate excitation temperature and column density values are determined. The latter were combined with the column density of the parent species NH2 to derive the deuterium fractionation in amidogen. We find a high deuteration level of amidogen radical in IRAS 16293-2422, with a deuterium enhancement about one order of magnitude higher than that predicted by earlier astrochemical models. Such a high enhancement can only be reproduced by a gas-grain chemical model if the pre-stellar phase preceding the formation of the protostellar system has a long duration: on the order of one million years. Conclusions. The amidogen D/H ratio measured in the low-mass protostar IRAS 16293-2422 is comparable to that derived for the related species imidogen and much higher than that observed for ammonia. Additional observations of these species will provide more insights into the mechanism of ammonia formation and deuteration in the ISM. Finally, we indicate the current possibilities to further explore these species at submillimeter wavelengths.

We report an extension toward the submillimeter domain of the laboratory spectroscopy of the syn and anti conformers of vinyl alcohol, a species that has been detected once in the interstellar medium, in the massive star-forming region Sagittarius B2(N) (Turner, B. E.; Apponi, A. Microwave detection of interstellar vinyl alcohol, CH2CHOH. Astrophys. J. 2001, 561, L207-L210, 10.1086/324762). Spectra were recorded with high accuracy (15-20 kHz) between 245 and 310 GHz by a frequency-modulation spectrometer equipped with a pyrolysis cell. Using these spectra and the refined molecular constants, we have searched for vinyl alcohol in the publicly available spectral line surveys from the ASAI [Astrochemical Surveys at Institut de Radioastronomie Millimétrique (IRAM)] Large Project, whose source sample spans the evolutionary range of a solar-type protostar and covering 75-350 GHz (4-1 mm) in frequency. We report non-detections in all nine sources, derive upper limits to the abundance of both conformers of vinyl alcohol, and comment on possible chemical and physical explanations for the non-detections.

Context. To date, several complex organic molecules have been detected in the interstellar medium, and they have been suggested as precursors of biologically important species. Propargylamine (HC ≡C−CH2−NH2) is structurally similar to a number of other organic molecules which have already been identified by radioastronomy, making it a good candidate for astrophysical detection. Aims. This work provides accurate rest frequencies of propargylamine, from the centimeter-wave to the submillimeter-wave region, useful to facilitate the detection of this molecule in the interstellar medium. Methods. An extensive laboratory study of the rotational spectrum of propargylamine has been performed using a pulsed-jet Fourier Transform Microwave (FTMW) spectrometer (7–19 GHz frequency range) and a frequency modulation microwave spectrometer (75–560 GHz). Several hundred rotational transitions of propargylamine were recorded in the ground and three lowest excited vibrational states. The experiments were supported by high-level ab initio computations, mainly employed to characterize the vibrational state structure and to predict spectroscopic parameters unknown prior to this study. Results. The measured transition frequencies yielded accurate rotational constants and the complete sets of quartic and sextic centrifugal distortion constants for propargylamine in its vibrational ground state. 14N-nuclear quadrupole coupling constants were also determined. Rotational and quartic centrifugal distortion constants were also obtained for the low-lying excited states v13 = 1 (A′), v20 = 1 (A″), and v21 = 1 (A″). The a-type Coriolis resonance which couples the v13 = 1 and v21 = 1 levels was analyzed. Conclusions. The determined spectroscopic constants allowed for the compilation of a dataset of highly accurate rest frequencies for astrophysical purposes in the millimeter and submillimeter regions with 1σ uncertainties that are smaller than 0.050 MHz, corresponding to 0.03 km s−1 at 500 GHz in radial equivalent velocity.

C-cyanomethanimine (HNCHCN), existing in the two $Z$ and $E$ isomeric forms, is a key prebiotic molecule, but, so far, only the $E$ isomer has been detected toward the massive star-forming region. Sagittarius B2(N) using transitions in the radio wavelength domain. With the aim of detecting HNCHCN in Sun-like-star forming regions, the laboratory investigation of its rotational spectrum has been extended to the millimeter-/submillimeter-wave (mm-/submm-) spectral window in which several unbiased spectral surveys have been already carried out. High-resolution laboratory measurements of the rotational spectrum of C-cyanomethanimine were carried out in the 100-420 GHz range using a frequency-modulation absorption spectrometer. We then searched for the C-cyanomethanimine spectral features in the mm-wave range using the high-sensitivity and unbiased spectral surveys obtained with the IRAM 30-m antenna in the ASAI context, the earliest stages of star formation from starless to evolved Class I objects being sampled. For both the $Z$ and $E$ isomers, the spectroscopic work has led to an improved and extended knowledge of the spectroscopic parameters, thus providing accurate predictions of the rotational signatures up to $\sim$700 GHz. So far, no C-cyanomethanimine emission has been detected toward the ASAI targets, and upper limits of the column density of $\sim$ 10$^{11}$--10$^{12}$ cm$^{-2}$ could only be derived. Consequently, the C-cyanomethanimine abundances have to be less than a few 10$^{-10}$ for starless and hot-corinos. A less stringent constraint, $\leq$ 10$^{-9}$, is obtained for shocks sites. The combination of the upper limits of the abundances of C-cyanomethanimine together with accurate laboratory frequencies up to $\sim$ 700 GHz poses the basis for future higher sensitivity searches around Sun-like-star forming regions., 9 pages, 4 figures, 2 tables. A&A accepted

Context: The $^{15}$N fractionation has been observed to show large variations among astrophysical sources, depending both on the type of target and on the molecular tracer used. These variations cannot be reproduced by the current chemical models. Aims: Until now, the $^{14}$N/$^{15}$N ratio in N$_2$H$^+$ has been accurately measured in only one prestellar source, L1544, where strong levels of fractionation, with depletion in $^{15}$N, are found ($^{14}$N/$^{15}$N$\: \approx 1000$). In this paper we extend the sample to three more bona fide prestellar cores, in order to understand if the antifractionation in N$_2$H$^+$ is a common feature of this kind of sources. Methods: We observed N$_2$H$^+$,N$^{15}$NH$^+$ and $^{15}$NNH$^+$ in L183, L429 and L694-2 with the IRAM 30m telescope. We modeled the emission with a non-local radiative transfer code in order to obtain accurate estimates of the molecular column densities, including the one for the optically thick N$_2$H$^+$. We used the most recent collisional rate coefficients available, and with these we also re-analysed the L1544 spectra previously published. Results: The obtained isotopic ratios are in the range $630-770$ and significantly differ with the value, predicted by the most recent chemical models, of $\approx 440$, close to the protosolar value. Our prestellar core sample shows high level of depletion of $^{15}$N in diazenylium, as previously found in L1544. A revision of the N chemical networks is needed in order to explain these results., Comment: Accepted for publication in A&A

Conventional absorption spectroscopy is still the workhorse in high-resolution rotational laboratory spectroscopy.1 The data obtained from these kind of instruments are relevant for astronomical searches of complex molecules that represent excellent probes of the physical and chemical environments and history of the sources where they are detected.2 Nowadays, observations performed by the Atacama Large Millimeter Array (ALMA) open up new opportunities to reveal the chemical complexity of solar systems analogues. At the same time the huge amount of data collected and the extremely rich surveys represent a challenge for the astrochemistry community. To reach this goal, the spectroscopic know-how is fundamental in recognizing typical pattern lines due to multiple internal interactions and motions that cause complicated energy level schemes, since the resulting spectra will be rather difficult to predict theoretically, mainly in the sub-mm wave region. For this reason a strong interplay between laboratory spectroscopists and observational astronomers is increasingly required to be able to unravel the experimental data. In this talk the features and the potential of the high resolution rotational spectroscopy technique will be pointed out, providing some results on different kind of molecules characterized by complex conformational landscapes. In particular, molecular spectra of potential astronomical interest will be presented, obtained using the free jet absorption millimeter wave and the free space cell absorption sub-mm wave spectrometers working at University of Bologna.3 References [1] S. Brünken, S. Schlemmer, arXiv:1605.07456, 2016 [2] E. Herbst, E. F. van Dishoeck, Annu. Rev. Astron. Astrophys. 47, 427, 2009 [3] C. Calabrese, A. Maris, L. Evangelisti, L. B. Favero, S. Melandri, W. Caminati, J. Phys. Chem. A. 117, 13712, 2013

The millimetre- and submillimetre-wave spectra of the five common isotopologues of (GeO)-O-16 in their electronic and vibrational ground state have been recorded in the spectral region 115-732GHz; for (GeO)-Ge-74-O-16, the rotational spectrum in the v = 1 state has been detected as well. Exploiting the high precision of the measurements, the Born-Oppenheimer breakdown parameter Delta(Ge)(01) could be determined from a Dunham analysis of the spectral data, whereas Delta(O)(01) was obtained from quantum-chemical calculations, because of the lack of high-precision measurements for the (GeO)-O-18 isotopologues. From the rotational equilibrium constant, the Born-Oppenheimer equilibrium distance of GeO could be determined.

Diacetylene (HC4H) is the simplest polyyne and has been the subject of several studies related to technology, materials, supramolecular chemistry, non-linear optics. It has been detected in space and in the atmosphere of Titan. Moreover, it is a model species to test sophisticated ab initio calculations. In this paper we report the study of the infrared spectrum of the rare isotopologue DC4D below 1000 cm−1. The experiment has been performed by high resolution Fourier transform infrared spectroscopy. The ν8 fundamental band, the ν 6 + ν 9 , ν 7 + ν 8 , and ν 6 + ν 8 combination bands and the ν 8 + ν 9 − ν 9 hot band have been observed and analysed, providing a set of accurate spectroscopic parameters. A global fit has also been performed in order to take into account the anharmonic resonance between the v 3 = 1 and the v 8 = v 9 = 1 states. The final results obtained from the global fit show a good improvement in the spectroscopic parameters for both the upper and lower states.

Context. Isotopic fractionation in dense molecular cores has been suggested as a possible origin of large 14N/15N ratio variations in solar system materials. While chemical models can explain some observed variations with different fractionation patterns for molecules with –NH or –CN functional groups, they fail to reproduce the observed ratios in diazenylium (N2H+). Aims. Observations of doubly 15N-substituted species could provide important constraints and insights for theoretical chemical models of isotopic fractionation. However, spectroscopic data are very scarce. Methods. The rotational spectra of the fully 15N-substituted isopologues of the diazenylium ion, 15N2H+ and 15N2D+, have been investigated in the laboratory well into the THz region by using a source-modulation microwave spectrometer equipped with a negative glow discharge cell. An extended chemical reaction network has been used to estimate what ranges of 15N fractionation in doubly 15N-substituted species could be expected in the interstellar medium (ISM). Results. For each isotopologue of the H- and D-containing pair, nine rotational transitions were accurately measured in the frequency region 88 GHz–1.2 THz. The analysis of the spectrum provided very precise rest frequencies at millimeter and sub-millimeter wavelengths, useful for the radioastronomical identification of the rotational lines of 15N2H+ and 15N2D+ in the ISM.

The pure rotational spectra of 13-C2HD and 12-C2HD were detected in the range 114-687 GHz. Lines belonging to the ground vibrational state were observed from J”=1 to J”=11. Several absorption lines were also detected in v4=1 (Π), v5=1 (Π), v4=2 (Σ and Δ), v5=2 (Σ and Δ), v4=v5=1 (Σ−, Σ+ and Δ), v4=3 (Π and Φ) and v5=3 (Π and Φ). The transitions detected in this work were fitted together with all the infrared lines available in literature for the bending states. The global fits allowed a very accurate determination of the spectroscopic parameters of these molecules.