Understanding the chemical complexity in Circumstellar Envelopes of C-Rich AGB stars: the case of IRC +10216

Agúndez, M.; Cernicharo, J.; Pardo, J. R.; Fonfría, J. P.; Guèlin, M.; Tenenbaum, E. D.; Ziurys, L. M.; Apponi, A. J.

doi:10.1007/s10509-007-9495-7

Cited by 27 publications

(17 citation statements)

References 18 publications

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“…The elucidation of the energetics and dynamics of elementary reactions of the simplest silicon-bearing radical, silylidyne (SiH; X 2 Π), with prototype hydrocarbon molecules under single collision conditions and the inherent formation of small organosilicon molecules is of core significance spanning astrochemistry, physical organic chemistry, and fundamental reaction dynamics. Considering astrochemical implications, an understanding of the chemical dynamics of silylidyne radical reactions with small hydrocarbon molecules is crucial to reveal the underlying molecular processes involved in the formation of organosilicon molecules in the interstellar medium [1][2][3][4]. These molecules are thought to play a key role in the formation of silicon carbide dust grains in the outflow of circumstellar envelopes of carbon rich Asymptotic Giant Branch (AGB) stars such as IRC+10216 holding temperatures up to a few 1,000 K close to the photosphere of the central star [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Untangling the reaction dynamics of the silylidyne radical (SiH; X2Π) with acetylene (C2H2; X1Σg+)

Yang

Dangi

Thomas

2016

Chemical Physics Letters

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Chemical reaction dynamics of silylidyne (SiH; X 2 Π) with acetylene (C 2 H 2 ; X 1 Σ g +) were studied exploiting the crossed molecular beam approach, and compared with previous studies on D1silylidyne with acetylene. The reaction is initiated by a barrierless addition of silylidyne to one or both carbons of acetylene leading to 1-sila-1-propene-1,3-diylidene and/or the cyclic 1silacyclopropenyl with the former isomerizing to the latter. 1-Silacyclopropenyl eventually loses atomic hydrogen yielding silacyclopropenylidene (c-SiC 2 H 2) in an overall exoergic reaction (experiment:-14.7 ± 8.5 kJ mol-1 ; theory:-13 ± 3 kJ mol-1). The enthalpy of formation for silacyclopropenylidene is determined to be 421.4 ± 9.3 kJ mol-1 .

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Section: Introductionmentioning

confidence: 99%

Untangling the reaction dynamics of the silylidyne radical (SiH; X2Π) with acetylene (C2H2; X1Σg+)

Yang

Dangi

Thomas

2016

Chemical Physics Letters

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“…This molecule was detected for the first time in the interstellar medium (ISM) in 1973 toward the Sagittarius B2 (Sgr B2) molecular cloud (Gardner & Winnewisser 1975). Since then, CH 2 CHCN has been detected toward different sources, such as Orion (Schilke et al 1997), the dark cloud TMC-1 (Matthews & Sears 1983), the circumstellar envelope of the late-type star IRC+10216 (Agúndez et al 2008), and the Titan atmosphere (Capone et al 1981). CH 2 CHCN is one of the molecules, whose high abundance and significant dipole moment allow radioastronomical detection even of its rare isotopologue species.…”

Section: Introductionmentioning

confidence: 99%

Laboratory characterization and astrophysical detection of vibrationally excited states of vinyl cyanide in Orion-KL

López

Tercero

Kisiel

et al. 2014

A&A

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Context. We perform a laboratory characterization in the 18-1893 GHz range and astronomical detection between 80-280 GHz in Orion-KL with IRAM-30 m of CH 2 CHCN (vinyl cyanide) in its ground and vibrationally excited states. Aims. Our aim is to improve the understanding of rotational spectra of vibrationally excited vinyl cyanide with new laboratory data and analysis. The laboratory results allow searching for these excited state transitions in the Orion-KL line survey. Furthermore, rotational lines of CH 2 CHCN contribute to the understanding of the physical and chemical properties of the cloud. Methods. Laboratory measurements of CH 2 CHCN made on several different frequency-modulated spectrometers were combined into a single broadband 50-1900 GHz spectrum and its assignment was confirmed by Stark modulation spectra recorded in the 18-40 GHz region and by ab-initio anharmonic force field calculations. For analyzing the emission lines of vinyl cyanide detected in Orion-KL we used the excitation and radiative transfer code (MADEX) at LTE conditions. Results. Detailed characterization of laboratory spectra of CH 2 CHCN in nine different excited vibrational states: 11 = 1, 15 = 1, 11 = 2, 10 = 1 ⇔ ( 11 = 1, 15 = 1), 11 = 3/ 15 = 2/ 14 = 1, ( 11 = 1, 10 = 1) ⇔ ( 11 = 2, 15 = 1), 9 = 1, ( 11 = 1, 15 = 2) ⇔ ( 10 = 1, 15 = 1) ⇔ ( 11 = 1, 14 = 1), and 11 = 4 are determined, as well as the detection of transitions in the 11 = 2 and 11 = 3 states for the first time in Orion-KL and of those in the 10 = 1 ⇔ ( 11 = 1, 15 = 1) dyad of states for the first time in space. The rotational transitions of the ground state of this molecule emerge from four cloud components of hot core nature, which trace the physical and chemical conditions of high mass star forming regions in the Orion-KL Nebula. The lowest energy vibrationally excited states of vinyl cyanide, such as 11 = 1 (at 328.5 K), 15 = 1 (at 478.6 K), 11 = 2 (at 657.8 K), the 10 = 1 ⇔ ( 11 = 1, 15 = 1) dyad (at 806.4/809.9 K), and 11 = 3 (at 987.9 K), are populated under warm and dense conditions, so they probe the hottest parts of the Orion-KL source. The vibrational temperatures derived for the 11 = 1, 11 = 2, and 15 = 1 states are 252 ± 76 K, 242 ± 121 K, and 227 ± 68 K, respectively; all of them are close to the mean kinetic temperature of the hot core component (210 K). The total column density of CH 2 CHCN in the ground state is (3.0 ± 0.9) × 10 15 cm −2 . We report the detection of methyl isocyanide (CH 3 NC) for the first time in Orion-KL and a tentative detection of vinyl isocyanide (CH 2 CHNC). We also give column density ratios between the cyanide and isocyanide isomers, obtaining a N(CH 3 NC)/N(CH 3 CN) ratio of 0.002. Conclusions. Laboratory characterization of many previously unassigned vibrationally excited states of vinyl cyanide ranging from microwave to THz frequencies allowed us to detect these molecular species in Orion-KL. Column density, rotational and vibrational temperatures for CH 2 CHCN in their ground and excited states, and the isotopolo...

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“…Acrylonitrile (CH 2 CHCN) was detected toward Sgr B2 by Gardner & Winnewisser (1975) and later also observed in the cold dark cloud TMC-1 by Matthews & Sears (1983). The molecule has recently been seen in the envelope of the carbonrich star IRC+10216 (Agúndez et al 2008). The protonated form of the molecule has been argued to exist in high abundances in the upper atmosphere of Titan based on a strong signal at m/z = 54 recorded by the ion-neutral-mass spectrometer (INMS) on board the Cassini spacecraft during a flyby on 2005 April 16 (Vuitton et al 2006).…”

Section: Introductionmentioning

confidence: 93%

THE DISSOCIATIVE RECOMBINATION OF PROTONATED ACRYLONITRILE, CH₂CHCNH⁺, WITH IMPLICATIONS FOR THE NITRILE CHEMISTRY IN DARK MOLECULAR CLOUDS AND THE UPPER ATMOSPHERE OF TITAN

Vigren

Hamberg

Zhaunerchyk

et al. 2009

ApJ

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Measurements on the dissociative recombination (DR) of protonated acrylonitrile, CH 2 CHCNH + , have been performed at the heavy ion storage ring CRYRING located in the Manne Siegbahn Laboratory in Stockholm, Sweden. It has been found that at ∼2 meV relative kinetic energy about 50% of the DR events involve only ruptures of X-H bonds (where X = C or N) while the rest leads to the production of a pair of fragments each containing two heavy atoms (alongside H and/or H 2). The absolute DR cross section has been investigated for relative kinetic energies ranging from ∼1 meV to 1 eV. The thermal rate coefficient has been determined to follow the expression k(T) = 1.78 × 10 −6 (T/300) −0.80 cm 3 s −1 for electron temperatures ranging from ∼10 to 1000 K. Gas-phase models of the nitrile chemistry in the dark molecular cloud TMC-1 have been run and results are compared with observations. Also, implications of the present results for the nitrile chemistry of Titan's upper atmosphere are discussed.

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Understanding the chemical complexity in Circumstellar Envelopes of C-Rich AGB stars: the case of IRC +10216

Cited by 27 publications

References 18 publications

Untangling the reaction dynamics of the silylidyne radical (SiH; X2Π) with acetylene (C2H2; X1Σg+)

Untangling the reaction dynamics of the silylidyne radical (SiH; X2Π) with acetylene (C2H2; X1Σg+)

Laboratory characterization and astrophysical detection of vibrationally excited states of vinyl cyanide in Orion-KL

THE DISSOCIATIVE RECOMBINATION OF PROTONATED ACRYLONITRILE, CH₂CHCNH⁺, WITH IMPLICATIONS FOR THE NITRILE CHEMISTRY IN DARK MOLECULAR CLOUDS AND THE UPPER ATMOSPHERE OF TITAN

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Understanding the chemical complexity in Circumstellar Envelopes of C-Rich AGB stars: the case of IRC +10216

Cited by 27 publications

References 18 publications

Untangling the reaction dynamics of the silylidyne radical (SiH; X2Π) with acetylene (C2H2; X1Σg+)

Untangling the reaction dynamics of the silylidyne radical (SiH; X2Π) with acetylene (C2H2; X1Σg+)

Laboratory characterization and astrophysical detection of vibrationally excited states of vinyl cyanide in Orion-KL

THE DISSOCIATIVE RECOMBINATION OF PROTONATED ACRYLONITRILE, CH2CHCNH+, WITH IMPLICATIONS FOR THE NITRILE CHEMISTRY IN DARK MOLECULAR CLOUDS AND THE UPPER ATMOSPHERE OF TITAN

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THE DISSOCIATIVE RECOMBINATION OF PROTONATED ACRYLONITRILE, CH₂CHCNH⁺, WITH IMPLICATIONS FOR THE NITRILE CHEMISTRY IN DARK MOLECULAR CLOUDS AND THE UPPER ATMOSPHERE OF TITAN