Detection Of HCN Research Articles

Four HD 209458 b transits through CRIRES+: Detection of H2O and non-detections of C2H2, CH4, and HCN

Context. HD 209458 b is one of the most studied exoplanets to date. Despite this, atmospheric characterisation studies yielded inconsistent species detections and abundances. Values reported for the C/O ratio range from ≈0.1 to 1.0. Of particular interest is the simultaneous detection of H2O and HCN reported by some studies using high-resolution ground-based observations, which would require the atmospheric C/O ratio to be fine-tuned to a narrow interval around 1. HCN has however not been detected from recent space-based observations. Aims. We aim to provide an independent study of HD 209458 b’s atmosphere with high-resolution observations, in order to infer the presence of several species, including H2O and HCN. Methods. We observed four primary transits of HD 209458 b at a high resolution (ℛ ≈ 92000) with CRIRES+ in the near infrared (band H, 1.431243–1.837253 μm). After reducing the data with pycrires, we prepared the data using the SysRem algorithm and performed a cross-correlation (CCF) analysis of the transmission spectra. We also compared the results with those obtained from simulated datasets constructed by combining the Exo-REM self-consistent model with the petitRADTRANS package. Results. Combining the four transits, we detect H2O with a signal-to-noise CCF metric of 8.7σ. This corresponds to a signal emitted at Kp = 151.3−23.4+31.1 km s−1 and blueshifted by −6−2+1 km s−1, consistent with what is expected for HD 209458 b. We do not detect any other species among C2H2, CH4, CO, CO2, H2S, HCN, and NH3. Comparing this with our simulated datasets, this result is consistent with a C/O ratio of 0.1 and an opaque cloud top pressure of 50 Pa, at a 3 times solar metallicity. This would also be consistent with recent JWST observations. However, none of the simulated results obtained with a bulk C/O ratio of 0.8, a value suggested by previous studies using GIANO-B and CRIRES, are consistent with our observations.

Detection of HCN and diverse redox chemistry in the plume of Enceladus

Detection of HCN and diverse redox chemistry in the plume of Enceladus

Water-rich Disks around Late M Stars Unveiled: Exploring the Remarkable Case of Sz 114

We present an analysis of the JDISCS JWST/MIRI-MRS spectrum of Sz 114, an accreting M5 star surrounded by a large dust disk with a shallow gap at ∼39 au. The spectrum is molecule-rich; we report the detection of water, CO, CO2, HCN, C2H2, and H2. The only identified atomic/ionic transition is from [Ne ii] at 12.81 μm. A distinct feature of this spectrum is the forest of water lines with the 17.22 μm emission surpassing that of most mid-to-late M star disks by an order of magnitude in flux and aligning instead with disks of earlier-type stars. Moreover, the flux ratios of C2H2/H2O and HCN/H2O in Sz 114 also resemble those of earlier-type disks, with a slightly elevated CO2/H2O ratio. While accretional heating can boost all infrared lines, the unusual properties of Sz 114 could be explained by the young age of the source, its formation under unusual initial conditions (a large massive disk), and the presence of dust substructures. The latter delays the inward drift of icy pebbles and helps preserve a lower C/O ratio over an extended period. In contrast, mid-to-late M-star disks—which are typically faint, small in size, and likely lack significant substructures—may have more quickly depleted the outer icy reservoir and already evolved out of a water-rich inner disk phase. Our findings underscore the unexpected diversity within mid-infrared spectra of mid-to-late M-star disks, highlighting the need to expand the observational sample for a comprehensive understanding of their variations and thoroughly test pebble drift and planet formation models.

XUE: Molecular Inventory in the Inner Region of an Extremely Irradiated Protoplanetary Disk

We present the first results of the eXtreme UV Environments (XUE) James Webb Space Telescope (JWST) program, which focuses on the characterization of planet-forming disks in massive star-forming regions. These regions are likely representative of the environment in which most planetary systems formed. Understanding the impact of environment on planet formation is critical in order to gain insights into the diversity of the observed exoplanet populations. XUE targets 15 disks in three areas of NGC 6357, which hosts numerous massive OB stars, including some of the most massive stars in our Galaxy. Thanks to JWST, we can, for the first time, study the effect of external irradiation on the inner (<10 au), terrestrial-planet-forming regions of protoplanetary disks. In this study, we report on the detection of abundant water, CO, 12CO2, HCN, and C2H2 in the inner few au of XUE 1, a highly irradiated disk in NGC 6357. In addition, small, partially crystalline silicate dust is present at the disk surface. The derived column densities, the oxygen-dominated gas-phase chemistry, and the presence of silicate dust are surprisingly similar to those found in inner disks located in nearby, relatively isolated low-mass star-forming regions. Our findings imply that the inner regions of highly irradiated disks can retain similar physical and chemical conditions to disks in low-mass star-forming regions, thus broadening the range of environments with similar conditions for inner disk rocky planet formation to the most extreme star-forming regions in our Galaxy.

Tailoring gas sensing properties of WS2 monolayer via Nb and Co embedding for highly sensitive and selective detection of HCN and H2S gases: a first principle study

We report on the adsorption performances of HCN, H2S, HF, and H2 gases on Nb and Co embedded WS2 monolayer using density functional theory calculations. The adsorption configurations, adsorption energy, charge transfer, density of state, band structure, and recovery time were studied to evaluate the possible tailoring of gas sensing properties to improve sensitivity and selectivity of the WS2 monolayer. The results show that HCN exhibits better adsorption on the Nb-embedded WS2 with an adsorption energy of −1.09 eV and charge transfer of −0.18 e, whereas H2S shows superior adsorption on the Co-embedded WS2 with an adsorption energy of −1.1 eV and charge transfer of 0.23 e. Better sensitivity and selectivity were recorded for the adsorption of the HCN and H2S on the Nb and Co-embedded WS2 monolayer respectively. At 398 K, the recovery times for the two sensing systems are 54 s and 61 s for Nb-embedded WS2 with HCN and Co-embedded WS2 with H2S respectively making them suitable for gas sensing applications. The study reveals the promising capabilities of Nb-embedded WS2 and Co-embedded WS2 in detecting HCN and H2S, respectively. In addition, it thoroughly investigates the influence of surface modifications on the characteristics of gas sensors.

Branching fraction measurement of the prompt-NO switch reaction NCN + H

The branching fraction ϕ of the prompt-NO switch reaction NCN + H (1), essentially yielding either CH + N2 (1a) or HCN + N (1b), is key for modeling prompt-NO formation in flames. Large discrepancies exist between available experimental data and flame modeling studies on the one hand and high-level theoretical predictions on the other hand, resulting in a factor of 5 uncertainty for ϕ1b at T=1500 K. By simultaneous monitoring of NCN and HCN concentration-time profiles during the reaction NCN + H at temperatures 1200K<T<2000K behind shock waves, ϕ1b has been directly measured for the first time. Thermal decomposition of cyanogen azide (NCN3) and ethyl iodide (C2H5I) served as sources for NCN radicals and H atoms. NCN has been detected by UV laser absorption at 329.130 nm and HCN detection was accomplished by mid-infrared frequency modulation spectroscopy at 3228.049cm−1. Kinetic simulations provided both the total rate constant k1 from the NCN and k1b from the HCN profiles. In order to account for a side reaction of residual BrCN from NCN3 synthesis, a rough estimate for the rate constant of the reaction BrCN + H was inferred from the experiments as well. The measured rate constants for k1 confirm earlier results (Faßheber et al., Phys. Chem. Chem. Phys. 16 (2014) 11647) and k1b follows the Arrhenius expression k1b/(cm3mol−1s−1)=4.2×1014exp(−38.2kJmol−1/RT) with moderate uncertainties of ±(37−49%). The branching fraction increases with temperature, yielding ϕ1b=0.22(±46%) at 1200 K, 0.47(±42%) at 1600 K, and 0.63(±53%) at 2000 K. The corresponding prompt-NO switch temperature of TS=1670K (ϕ1b=0.5) shows that the reaction NCN + H advances toward the Fenimore products HCN + N already at typical temperatures of hydrocarbon/air flames, in stark contrast to the most recent theoretical estimate reporting TS=3235K.

Circumnuclear dense gas disk fuelling the active galactic nucleus in the nearby radio galaxy NGC 4261

The cold molecular gas in the circumnuclear disk (CND) of radio galaxies provides critical information for understanding the mass accretion onto active galactic nuclei. We present the first detection and maps of HCNJ= 1–0 and HCO+J= 1–0 emission lines from the circumnuclear region of a nearby radio galaxy, NGC 4261, using the Northern Extended Millimeter Array. Both molecular lines are detected at a radial velocity of ±700 km s−1relative to the systemic velocity of the galaxy, and they arise from a CND with an outer radius of 100 pc. The velocity fields of HCN and HCO+are fitted with a Keplerian disk rotation. The enclosed mass is (1.6 ± 0.1) × 109 M⊙, assuming a disk inclination angle of 64°. The continuum image at 80 GHz reveals a weak two-sided jet structure extending over 5 kpc along the east–west direction and a bright core at the centre. The continuum spectrum between 80 and 230 GHz shows a spectral index of −0.34 ± 0.02, which suggests optically thin synchrotron radiation. The dense gas mass associated with the CND is calculated to be 6.03 × 107 M⊙. It supports a positive correlation between the dense gas mass in the CND and the accretion rate onto the supermassive black hole, though there are uncertainties in the parameters of the correlation.

Molecular tracers of planet formation in the atmospheres of hot Jupiters

ABSTRACT The atmospheric chemical composition of a hot Jupiter can lead to insights into where in its natal protoplanetary disc it formed and its subsequent migration pathway. We use a 1D chemical kinetics code to compute a suite of models across a range of elemental abundances to investigate the resultant abundances of key molecules in hot Jupiter atmospheres. Our parameter sweep spans metallicities between 0.1x and 10x solar values for the C/H, O/H, and N/H ratios, and equilibrium temperatures of 1000 and 2000 K. We link this parameter sweep to the formation and migration models from previous works to predict connections between the atmospheric molecular abundances and formation pathways, for the molecules H2O, CO, CH4, CO2, HCN, and NH3. We investigate atmospheric H2O abundances in eight hot Jupiters reported in the literature. All eight planets fall within our predicted ranges for various formation models; however, six of them are degenerate between multiple models and hence require additional molecular detections for constraining their formation histories. The other two planets, HD 189733 b and HD 209458 b, have water abundances that fall within ranges expected from planets that formed beyond the CO2 snowline. Finally, we investigate the detections of H2O, CO, CH4, CO2, HCN, and NH3 in the atmosphere of HD 209458 b and find that, within the framework of our model, the abundances of these molecules best match with a planet that formed between the CO2 and CO snowlines and then underwent disc-free migration to reach its current location.

Adsorption of HCN on WSe2 monolayer doped with transition metal (Fe, Ag, Au, As and Mo)

In this paper, the adsorption performances for HCN upon pure and metal (Fe, Ag, Au, As and Mo) doped WSe2 monolayers are analyzed on the ground of the density functional theory (DFT) and the best sites of doping are assumed. The adsorption performance of intrinsic WSe2, Fe-WSe2, Ag-WSe2, Au-WSe2 and Mo-WSe2 to HCN molecule were simulated according to the charge transfer, DOS and molecular orbital. The results manifest that all metal (Fe, Ag, Au, As and Mo) doped WSe2 monolayers have better adsorption properties for HCN. Nevertheless, occurrence of chemisorption only exists in HCN/Mo-WSe2 system, indicating this system might be candidate materials for the adsorption of HCN. Besides, after adsorption, the conductivity of all systems changes a lot, meaning that monitoring conductivity change of all systems above could be a method to sensing HCN. Thus, all metal (Fe, Ag, Au, As and Mo) doped WSe2 could be favorable materials for HCN detection.

Quantitative and Sensitive Mid-Infrared Frequency Modulation Detection of HCN behind Shock Waves

Despite its key role for the study and modeling of nitrogen chemistry and NOx formation in combustion processes, HCN has only rarely been detected under high-temperature conditions. Here, we demonstrate quantitative detection of HCN behind incident and reflected shock waves using a novel sensitive single-tone mid-infrared frequency modulation (mid-IR-FM) detection scheme. The temperature-dependent pressure broadening of the P(26) line in the fundamental CH stretch vibration band was investigated in the temperature range 670K≤T≤1460K, yielding a pressure broadening coefficient for argon of 2γAr296K=(0.093±0.007)cm−1atm−1 and a temperature exponent of nAr=0.67±0.07. The sensitivity of the detection scheme was characterized by means of an Allan analysis, showing that HCN detection on the ppm mixing ratio level is possible at typical shock wave conditions. In order to demonstrate the capability of mid-IR-FM spectroscopy for future high-temperature reaction kinetic studies, we also report the first successful measurement of a reactive HCN decay profile induced by its reaction with oxygen atoms.

Pluto’s atmosphere observations with ALMA: Spatially-resolved maps of CO and HCN emission and first detection of HNC

Pluto exhibits a tenuous, predominantly N2-CH4 atmosphere, with Titan-like chemistry. Previous observations with ALMA have permitted the detection of CO and HCN at 345.796 and 354.505 GHz in this atmosphere, yielding vertically resolved chemical and thermal information. We report on new observations of Pluto’s atmosphere with ALMA, performed in April and July/August 2017 with two main goals: (i) obtaining spatially-resolved measurements (∼0.06” on the ∼0.15” disk subtended by Pluto and its atmosphere) of CO(3-2) and HCN(4-3) (ii) targetting new chemical compounds, primarily hydrogen isocyanide (HNC) . These observations are modeled with radiative transfer codes coupled with inversion methods. The CO line shows an absorption core at beam positions within Pluto’s disk, a direct signature of Pluto’s cold mesosphere. Analysis of the CO line map provides tentative evidence for a non-uniform temperature field in the lower atmosphere (near 30 km), with summer pole latitudes being 7 ± 3.5 K warmer than low latitudes. This unexpected result may point to shorter radiative timescales in the atmosphere than previously thought. The HCN emission is considerably more extended than CO, peaking at radial distances beyond Pluto limb, and providing a new method to determine Pluto’s HCN vertical profile in 2017. The mean (column-averaged) location of HCN is at 690 ± 75 km altitude, with an upper atmosphere (>800 km) mixing ratio of ∼1.8×10−4. Little or no HCN (<5 × 10−9 at 65 km) is present in the lower atmosphere, implying undersaturation of HCN there. The HCN emission appears enhanced above the low-latitude limb, but interpretation, in terms of an enhanced HCN abundance or a warmer upper atmosphere there, is uncertain. The first detection of HNC is reported, with a (7.0 ± 2.1)×1012 cm−2 column density, referred to Pluto surface, and a HNC/HCN ratio of 0.095 ± 0.026, very similar to their values in Titan’s atmosphere. We also obtain upper limits on CH3CN (<2.6×1013 cm−2) and CH3CCH (<8.5×1014 cm−2); the latter value is inconsistent with the reported detection of CH3CCH from New Horizons. These upper limits also point to incomplete resublimation of ice-coated aerosols in the lower atmosphere.

Two‐dimensional CoOOH as a Highly Sensitive and Selective H2S, HCN and HF Gas Sensor: A Computational Investigation

AbstractUsing density functional theory, we have systematically investigate the room temperature gas‐sensing performance of two‐dimensional delafossite cobalt oxyhydroxide (CoOOH) sheets as H2S, HCN and HF detection. Our findings show that CoOOH is sensitive to H2S, HCN and HF gas by a physisorption interaction. The CoOOH sheets exhibit significant changes after the gas molecules adsorption, particularly its electrical conductivity. The suitable adsorption energy, which guarantees short recovery time, remarkable high sensitivity and selectivity, appreciable work function change and sharply enhanced electrical conductivity make CoOOH sheets as an effective nanosensor for toxic H2S, HCN and HF gases detection.

Studying star-forming processes at core and clump scales: the case of the young stellar object G29.862−0.0044

Aims. To advance our knowledge of star formation, in addition to statistical studies and large surveys of young stellar objects (YSOs), it is important to carry out detailed studies towards particular objects. Given that massive molecular clumps fragment into cores where star formation takes place, these kinds of studies should be done on different spatial scales. The aim of this work is to investigate the star-forming processes at core and clump scales. Methods. Using near-infrared (NIR) data obtained with NIRI at the Gemini-North telescope, data of the complex molecular species CH3OCHO and CH3CN obtained from the Atacama Large Millimeter Array (ALMA) database, observations of HCN, HNC, HCO+, and C2H carried out with the Atacama Submillimeter Telescope Experiment (ASTE), and CO data from public surveys observed with the James Clerck Maxwell Telescope (JCMT), we perform a deep study of the YSO G29.862−0.0044 (YSO-G29) at core and clump spatial scales. Results. The NIR emission shows that YSO-G29 is composed of two nebulosities separated by a dark lane, suggesting a scenario consistent with a typical disc plus jets system, albeit in this case highly asymmetric. The northern nebulosity is open, diffuse, and is divided into two branches, while the southern one is smaller and sharper. They are likely produced by the scattered light in cavities carved out by jets or winds on an infalling envelope of material, which also presents line emission of H2 S(1) 1–0 and 2–1, and [FeII]. The presence of the complex molecular species observed with ALMA confirms that we are mapping a hot molecular core. The CH3CN emission concentrates at the position of the dark lane and appears slightly elongated from southwest to northeast in agreement with the inclination of the system as observed in the NIR. The morphology of the CH3OCHO emission is more complex and extends along some filaments and concentrates in knots and clumps, mainly southwards of the dark lane, suggesting that the southern jet is encountering a dense region. The northern jet is able to flow more freely, generating the more extended features as seen in the NIR. This is in agreement with the redshifted molecular outflow traced by the 12CO J = 3–2 line extending towards the northwest and the lack of a blueshifted outflow. This configuration can be explained by considering that G29-YSO is located at the furthest edge of the molecular clump along the line of sight, which is consistent with the position of the source in the cloud mapped in the C18O J = 3–2 line. The detection of HCN, HNC, HCO+, and C2H allowed us to characterise the dense gas at clump scales, yielding results that are in agreement with the presence of a high-mass protostellar object.

High-resolution mass spectrometry for future space missions: Comparative analysis of complex organic matter with LAb-CosmOrbitrap and laser desorption/ionization Fourier transform ion cyclotron resonance.

Mass spectrometers are regularly boarded on spacecraft for the exploration of the Solar System. A better understanding of the origin, distribution and evolution of organic matter and its relationships with inorganic matter in different extra-terrestrial environments requires the development of innovative space tools, described as Ultra-High-Resolution Mass Spectrometry (UHRMS) instruments. Analyses of a complex organic material simulating extraterrestrial matter (Titan's tholins) are performed with a homemade space-designed Orbitrap™ equipped with a laser ablation ionization source at 266 nm: the LAb-CosmOrbitrap. Mass spectra are obtained using only one laser shot and transient duration of 838 ms. A comparison is made on the same sample with a laboratory benchmark mass spectrometer: a Fourier Transform Ion Cyclotron Resonance equipped with a laser desorption ionization source at 355 nm (LDI-FTICR) allowing accumulation of 20,000 laser shots. Mass spectra and attributions of molecular formulae based on the peaks detected by both techniques show significant similarities. Detection and identification of the same species are validated. The formation of clusters ions with the LAb-CosmOrbitrap is also presented. This specific feature brings informative and unusual indirect detections about the chemical compounds constituting Titan's tholins. In particular, the detection of HCN confirms previous results obtained with laboratory Electrospray Ionization (ESI)-UHRMS studies about the understanding of polymeric patterns for the formation of tholins. The capabilities of the LAb-CosmOrbitrap to decipher complex organic mixtures using single laser shot and a short transient are highlighted. In agreement with results provided by a commercial FTICR instrument in the laboratory, we demonstrate in this work the relevance of a space laser-CosmOrbitrap instrument for future planetary exploration.

Hydrogen cyanide sensor based on the porphyrin-like B4-doped [60]-fullerenes: a DFT study

Using density functional theory calculations, a porous C60 fullerene with B4 porphyrin-like cavity (C54B4) is designed, and its potential application is investigated in the HCN detection. The formation energy is predicted to be about − 155.5 kcal/mol, which is comparable with that of C54N4 nanocage (~ − 156.1 kcal/mol) and is somewhat less negative than that of [60] fullerene (~ − 161.0 kcal/mol). The C54B4 nanocage shows much higher electrical conductivity compared to the C60 and C54N4 nanocages. We found that the HCN adsorbs on the C54B4 nanocage via two different mechanisms, including vertical adsorption from its N-head and horizontal adsorption with N–C bond. These mechanisms differently affect the electronic properties of C54B4. The most stable HCN/C54B4 complex is that in which the HCN molecule lies on the center of B4 cavity so that each C or N atom is in connection with two B atoms with adsorption energy of about − 73.5 kcal/mol. Upon the HCN adsorption, a large charge transfer about 0.33 e and a great gap opening about 1.56 eV occurred for C54B4, which sharply increases the electrical resistance of C54B4, but its effect on work function is negligible. Thus, we concluded that C54B4 may be a promising electronic sensor for the HCN gas.

A chemical kinetics code for modelling exoplanetary atmospheres

Chemical compositions of exoplanets can provide key insights into their physical processes, and formation and evolutionary histories. Atmospheric spectroscopy provides a direct avenue to probe exoplanetary compositions. However, whether obtained in transit or thermal emission, spectroscopic observations probe limited pressure windows of planetary atmospheres and are directly sensitive to only a limited set of spectroscopically active species. It is therefore critical to have chemical models that can relate retrieved atmospheric compositions to an atmosphere's bulk physical and chemical state. To this end we present LEVI, a new chemical kinetics code for modelling exoplanetary atmospheres. LEVI calculates the gas phase hydrogen, oxygen, carbon, and nitrogen chemistry in planetary atmospheres. Here we focus on hot gas giants. Applying LEVI, we investigate how variations in bulk C/O and N/O affects the observable atmospheric chemistry in hot Jupiters. For typical hot Jupiters we demonstrate the strong sensitivity of molecular detections to the atmospheric C/O. Molecular detections are conversely less sensitive to the atmospheric N/O ratio, although highly super-solar N/O can decrease the C/O required for HCN and NH3 detection. Using a new P-T profile for HD 209458b without a thermal inversion, we evaluate recently reported detection's of CO, H2O and HCN in its day-side atmosphere. We find that our models are consistent with the detected species, albeit with a narrow compositional window around C/O $\sim$ 1. A C/O $\gtrsim$ 0.9 (1.6 times solar) was required to meet the minimum reported value for HCN, while a C/O $\lesssim$ 1 (1.8 times solar) was required to fit the nominal H2O abundance.

A new radio molecular line survey of planetary nebulae

Certain planetary nebulae (PNe) contain shells, filaments, or globules of cold gas and dust whose heating and chemistry are likely driven by UV and X-ray emission from their central stars and from wind-collision-generated shocks. We present the results of a survey of molecular line emission in the 88–236 GHz range from nine nearby (&lt;1.5 kpc) planetary nebulae spanning a range of UV and X-ray luminosities, using the 30 m telescope of the Institut de Radioastronomie Millimétrique. Rotational transitions of thirteen molecules, including CO isotopologues and chemically important trace species, were observed and the results compared with and augmented by previous studies of molecular gas in PNe. Lines of the molecules HCO+, HNC, HCN, and CN, which were detected in most objects, represent new detections for four planetary nebulae in our study. Specifically, we present the first detections of 13CO (1–0, 2–1), HCO+, CN, HCN, and HNC in NGC 6445; HCO+ in BD+30°3639; 13CO (2–1), CN, HCN, and HNC in NGC 6853; and 13CO (2–1) and CN in NGC 6772. Flux ratios were analyzed to identify correlations between the central star and/or nebular UV and X-ray luminosities and the molecular chemistries of the nebulae. This analysis reveals a surprisingly robust dependence of the HNC/HCN line ratio on PN central star UV luminosity. There exists no such clear correlation between PN X-rays and various diagnostics of PN molecular chemistry. The correlation between HNC/HCN ratio and central star UV luminosity demonstrates the potential of molecular emission line studies of PNe for improving our understanding of the role that high-energy radiation plays in the heating and chemistry of photodissociation regions.

Boosting BeONT Reactivity with HCN by Calcium and Magnesium Doping: A DFT Investigation of Electronic Structure, AIM, NMR, NQR and NBO Analysis

Adsorption of the HCN molecule is very important in environment and industrial applications. The BeONT may be good candidate for HCN capture because of large surface. Unfortunately, BeONT shows limited HCN detection. Therefore, we investigate the possibility of HCN adsorption on Ca and Mg-doped BeONT by density functional theory calculations. It was found that HCN adsorption on doped nanotube has relatively higher adsorption energy as compared with the perfect one. Furthermore, there exists a strong adsorption between HCN molecule and doped nanotubes, which exhibited more active interaction and larger net charge transfer than that of pristine nanotube. As well as, calculated geometrical parameters and electronic properties for studied systems indicate that the Ca-doped BeONT and Mg-doped BeONT present high sensitivity to HCN, compared with the pristine BeONT. Theoretical results reveal that the adsorption of the HCN on the doped nanotube is influenced on the electronic conductance of the doped-BeONT. Therefore, Ca and Mg-doped nanotube can be considered as promising sensor for detecting HCN molecule. According to NBO analysis, electron flow is spontaneous from doped nanotube to HCN molecule.

Exploring the volatile composition of comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON) with ALMA

Comets formed in the outer and cold parts of the disk which eventually evolved into our Solar System. Assuming that the comets have undergone no major processing, studying their composition provides insight in the pristine composition of the Solar Nebula. We derive production rates for a number of volatile coma species and explore how molecular line ratios can help constrain the uncertainties of these rates. We analyse observations obtained with the Atacama Large Millimetre/Submillimetre Array of the volatile composition of the comae of comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON) at heliocentric distances of ~1.45 AU and ~0.56 AU, respectively. Assuming a Haser profile with constant outflow velocity, we model the line intensity of each transition using a 3D radiative transfer code and derive molecular production rates and parent scale lengths. We report the first detection of CS in comet ISON obtained with the ALMA array and derive a parent scale length for CS of ~200 km. Due to the high spatial resolution of ALMA, resulting in a synthesised beam with a size slightly smaller than the derived parent scale length, we are able to tentatively identify CS as a daughter species, i.e., a species produced in the coma and/or sublimated from icy grains, rather than a parent species. In addition we report the detection of several CH3OH transitions and confirm the previously reported detections of HCN, HNC and H2CO as well as dust in the coma of each comet, and report 3sigma upper limits for HCO+. We derive molecular production rates relative to water of 0.2% for CS, 0.06-0.1% for HCN, 0.003-0.05% for HNC, 0.1-0.2% for H2CO and 0.5-1.0% for CH3OH, and show that the modelling uncertainties due to unknown collision rates and kinematic temperatures are modest and can be mitigated by available observations of different transitions of HCN.

The M12N12 (M = Al, Ga) clusters as potential sensors for NO, NO2 and HCN detection

The geometries, energies and electronic properties of NO, NO2 and HCN molecules adsorption on the M12N12 (M =Al, Ga) clusters have been studied by using density functional theory in order to find novel sensors for NO, NO2 and HCN detection. We find that the three molecules can be chemisorbed on the M12N12 (M = Al, Ga) clusters with reasonable adsorption energies (−0.503 to −1.377 eV). It is clear that there are optimal charge transfers between the clusters and molecules. The HOMO-LUMO gaps of the M12N12 clusters are very sensitive to the presence of the NO, NO2 and HCN molecules. Due to the reasonable adsorption energies and the changes of electronic properties accompanied with the apparent charge transfer, the M12N12 (M = Al, Ga) clusters are potentially good NO, NO2 and HCN sensors.