Ab initio calculations on molecules of interest to interstellar cloud chemistry

Botschwina, Peter; Horn, Matthias; Flügge, J.; Seeger, S.

doi:10.1039/ft9938902219

Cited by 122 publications

(96 citation statements)

References 69 publications

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“…Excluding IM Lup, an extremely large and massive disk, from the sample gives a much narrower range of 3.1 − 5.4 Jy km s −1 and 0.4 − 1.4 Jy km s −1 for HCO + J = 3 − 2 and N 2 H + J = 3 − 2, respectively. To calculate the line fluxes for our model we use the line transfer module of PRODIMO ) and the molecular data from the Leiden Atomic and Molecular Database (Schöier et al 2005;Botschwina et al 1993;Flower 1999). For our reference model CI_XN we find fluxes of 2.4 Jy km s −1 and 0.78 Jy km s −1 for HCO + J = 3 − 2 and N 2 H + J = 3 − 2, respectively.…”

Section: Appendix E: Comparison To Observationsmentioning

confidence: 99%

Stellar energetic particle ionization in protoplanetary disks around T Tauri stars

Rab

Güdel

Padovani

et al. 2017

A&A

102

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Context. Anomalies in the abundance measurements of short lived radionuclides in meteorites indicate that the protosolar nebulae was irradiated by a high amount of energetic particles (E 10 MeV). The particle flux of the contemporary Sun cannot explain these anomalies. However, similar to T Tauri stars the young Sun was more active and probably produced enough high energy particles to explain those anomalies. Aims. We want to study the interaction of stellar energetic particles with the gas component of the disk (i.e. ionization of molecular hydrogen) and identify possible observational tracers of this interaction. Methods. We use a 2D radiation thermo-chemical protoplanetary disk code to model a disk representative for T Tauri stars. We use a particle energy distribution derived from solar flare observations and an enhanced stellar particle flux proposed for T Tauri stars. For this particle spectrum we calculate the stellar particle ionization rate throughout the disk with an accurate particle transport model. We study the impact of stellar particles for models with varying X-ray and cosmic-ray ionization rates. Results. We find that stellar particle ionization has a significant impact on the abundances of the common disk ionization tracers HCO + and N 2 H + , especially in models with low cosmic-ray ionization rates (e.g. 10 −19 s −1 for molecular hydrogen). In contrast to cosmic rays and X-rays, stellar particles cannot reach the midplane of the disk. Therefore molecular ions residing in the disk surface layers are more affected by stellar particle ionization than molecular ions tracing the cold layers/midplane of the disk. Conclusions. Spatially resolved observations of molecular ions tracing different vertical layers of the disk allow to disentangle the contribution of stellar particle ionization from other competing ionization sources. Modeling such observations with a model like the one presented here allows to constrain the stellar particle flux in disks around T Tauri stars.

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Section: Appendix E: Comparison To Observationsmentioning

confidence: 99%

Stellar energetic particle ionization in protoplanetary disks around T Tauri stars

Rab

Güdel

Padovani

et al. 2017

A&A

102

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“…More difficult is the task of determining the total column densities of the corresponding molecules since, depending on the excitation conditions T kin , n(H 2 )), the observed levels may represent only a small fraction of the total column density. However, SiO and HCO + have very similar dipole moments, namely 3.1 (Raymonda et al 1970) and 3.9 Debye (Botschwina et al 1993), and therefore their excitation conditions expressed in terms of critical density should be similar.…”

Section: The Spatial and Velocity Distributions Of The Spectral Line mentioning

confidence: 99%

A survey of the Galactic center region in HCO⁺, H¹³CO⁺, and SiO

Riquelme

Bronfman

Mauersberger

et al. 2010

A&A

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Aims. A large-scale survey of the Galactic center region in the 3 mm rotational transitions of SiO, HCO + and H 13 CO + (beamsize ∼3. 6) was conducted to provide an estimate of cloud conditions, heating mechanisms, chemistry, and other properties. Methods. Using the NANTEN 4 m telescope from Nagoya University, a region between −5. • 75 < l < 5.• 6 and −0.• 68 < b < 1.• 3 was mapped in the J = 1 → 0 lines of HCO + and H 13 CO + and in the J = 2 → 1 line of SiO with a spacing of 3. 75 (HCO + ) and 1. 875 (SiO and H 13 CO + ). Results. Velocity channel maps, longitude-velocity maps, and latitude-velocity maps are presented. We identify 51 molecular clouds; 33 of them belong to the Galactic center and 18 to disk gas. We derive an average of the luminosity ratio of SiO(J = 2 → 1)/CO(J = 1 → 0) in clouds belonging to the Galactic center of 4.9 × 10 −3 and for disk clouds of 3.4 × 10 −3 . The luminosity ratio of HCO + (J = 1 → 0)/CO(J = 1 → 0) in the Galactic center is 3.5 × 10 −2 , and for disk clouds it is 1.5 × 10 −2 . We can distinguish clearly between regions where the SiO or HCO + dominate.

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“…It was first observed in the interstellar medium (ISM) in 1970 by Buhl and Snyder 1 right on the tail of the first confirmed detection of the ubiquitous and highly significant related molecule, carbon monoxide. 2 HCO + is now known to be one of the most abundant interstellar molecules and is often used as a spectroscopic probe due to its large dipole moment (∼3.9 D) [3][4][5] and shift of rotational lines as compared to CO. The high abundance of these molecules in the ISM leads one to wonder if a van der Waals complex could be formed between the two since both have enough internal charge separation to form such and proton exchange would be fairly rapid.…”

Section: Introductionmentioning

confidence: 99%

Communication: Spectroscopic consequences of proton delocalization in OCHCO+

Fortenberry

Mancini

et al. 2015

The Journal of Chemical Physics

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Quartic force field-derived vibrational frequencies and spectroscopic constants for the isomeric pair SNO and OSN and isotopologues The Journal of Chemical Physics 143, 084308 (2015) Even though quartic force fields (QFFs) and highly accurate coupled cluster computations describe the OCHCO + cation at equilibrium as a complex between carbon monoxide and the formyl cation, two notable and typical interstellar and atmospheric molecules, the prediction from the present study is that the equilibrium C ∞v structure is less relevant to observables than the saddle-point D ∞h structure. This is the conclusion from diffusion Monte Carlo and vibrational self-consistent field/virtual state configuration interaction calculations utilizing a semi-global potential energy surface. These calculations demonstrate that the proton "rattle" motion (ν 6 ) has centrosymmetric delocalization of the proton over the D ∞h barrier lying only 393.6 cm −1 above the double-well OCHCO + C ∞v minima. As a result, this molecule will likely appear D ∞h , and the rotational spectrum will be significantly dimmer than the computed equilibrium 2.975 D center-of-mass dipole moment indicates. However, the proton transfer fundamental, determined to be at roughly 300 cm −1 , has a very strong intensity. This prediction as well as those of other fundamentals should provide useful guides for laboratory detection of this cation. Finally, it is shown that the two highest energy QFF-determined modes are actually in good agreement with their vibrational configuration interaction counterparts. These high-level quantum chemical methods provide novel insights into this fascinating and potentially common interstellar molecule. C 2015 AIP Publishing LLC. [http://dx

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Ab initio calculations on molecules of interest to interstellar cloud chemistry

Abstract: Making use of CEPA-1, CCSD and CCSD(T) calculations with relatively large basis sets and taking the major anharmonicity effects into account, predictions are made for the following 12 molecules which are of interest to interstellar cloud chemistry: HC;

Cited by 122 publications

References 69 publications

Stellar energetic particle ionization in protoplanetary disks around T Tauri stars

Stellar energetic particle ionization in protoplanetary disks around T Tauri stars

A survey of the Galactic center region in HCO⁺, H¹³CO⁺, and SiO

Communication: Spectroscopic consequences of proton delocalization in OCHCO+

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Ab initio calculations on molecules of interest to interstellar cloud chemistry

Abstract: Making use of CEPA-1, CCSD and CCSD(T) calculations with relatively large basis sets and taking the major anharmonicity effects into account, predictions are made for the following 12 molecules which are of interest to interstellar cloud chemistry: HC;

Cited by 122 publications

References 69 publications

Stellar energetic particle ionization in protoplanetary disks around T Tauri stars

Stellar energetic particle ionization in protoplanetary disks around T Tauri stars

A survey of the Galactic center region in HCO+, H13CO+, and SiO

Communication: Spectroscopic consequences of proton delocalization in OCHCO+

Contact Info

Product

Resources

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A survey of the Galactic center region in HCO⁺, H¹³CO⁺, and SiO