Detection of Ketenimine (CH
                    <sub>2</sub>
                    CNH) in Sagittarius B2(N) Hot Cores

Lovas, Francis J.; Hollis, J. M.; Remijan, Anthony J.; Jewell, P. R.

doi:10.1086/506324

Cited by 91 publications

(89 citation statements)

References 18 publications

(19 reference statements)

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“…Assuming the same source size and temperature and a linewidth (FWHM) of 20 km s −1 , our spectral survey at 3 mm yields a column-density upper limit of 2 × 10 16 cm −2 toward Sgr B2(N), which is less constraining than the detection reported by Lovas et al (2006).…”

Section: Ketenimine Ch 2 Cnhmentioning

confidence: 70%

“…The first detection of ketenimine was claimed by Lovas et al (2006) toward Sgr B2(N) based on GBT observations of three lines in absorption, with lower-level energies ranging from 33 to 50 K. Assuming a source size of 5 , they derive an excitation temperature of 65 K and a column density of ∼1.5 × 10 16 cm −2 , with an uncertainty of a factor of two. Assuming the same source size and temperature and a linewidth (FWHM) of 20 km s −1 , our spectral survey at 3 mm yields a column-density upper limit of 2 × 10 16 cm −2 toward Sgr B2(N), which is less constraining than the detection reported by Lovas et al (2006).…”

Section: Ketenimine Ch 2 Cnhmentioning

confidence: 99%

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Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)

Беллоче

Müller

Menten

et al. 2013

A&A

385

523

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Context. The discovery of amino acids in meteorites fallen to Earth and the detection of glycine, the simplest of them, in samples returned from a comet to Earth strongly suggest that the chemistry of the interstellar medium is capable of producing such complex organic molecules and that they may be widespread in our Galaxy. Aims. Our goal is to investigate the degree of chemical complexity that can be reached in the interstellar medium, in particular in dense star-forming regions. Methods. We performed an unbiased, spectral line survey toward Sgr B2(N) and (M), two regions where high-mass stars are formed, with the IRAM 30 m telescope in the 3 mm atmospheric transmission window. Partial surveys at 2 and 1.3 mm were performed in parallel. The spectra were analyzed with a simple radiative transfer model that assumes local thermodynamic equilibrium but takes optical depth effects into account. Results. About 3675 and 945 spectral lines with a peak signal-to-noise ratio higher than 4 are detected at 3 mm toward Sgr B2(N) and (M), i.e. about 102 and 26 lines per GHz, respectively. This represents an increase by about a factor of two over previous surveys of Sgr B2. About 70% and 47% of the lines detected toward Sgr B2(N) and (M) are identified and assigned to 56 and 46 distinct molecules as well as to 66 and 54 less abundant isotopologues of these molecules, respectively. In addition, we report the detection of transitions from 59 and 24 catalog entries corresponding to vibrationally or torsionally excited states of some of these molecules, respectively, up to a vibration energy of 1400 cm −1 (2000 K). Excitation temperatures and column densities were derived for each species but should be used with caution. The rotation temperatures of the detected complex molecules typically range from ∼50 to 200 K. Among the detected molecules, aminoacetonitrile, n-propyl cyanide, and ethyl formate were reported for the first time in space based on this survey, as were five rare isotopologues of vinyl cyanide, cyanoacetylene, and hydrogen cyanide. We also report the detection of transitions from within twelve new vibrationally or torsionally excited states of known molecules. Absorption features produced by diffuse clouds along the line of sight are detected in transitions with low rotation quantum numbers of many simple molecules and are modeled with ∼30-40 velocity components with typical linewidths of ∼3-5 km s −1 . Conclusions. Although the large number of unidentified lines may still allow future identification of new molecules, we expect most of these lines to belong to vibrationally or torsionally excited states or to rare isotopologues of known molecules for which spectroscopic predictions are currently missing. Significant progress in extending the inventory of complex organic molecules in Sgr B2(N) and deriving tighter constraints on their location, origin, and abundance is expected in the near future thanks to an ongoing spectral line survey at 3 mm with ALMA in its cycles 0 and 1. The present single-dish surve...

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Section: Ketenimine Ch 2 Cnhmentioning

confidence: 70%

Section: Ketenimine Ch 2 Cnhmentioning

confidence: 99%

Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)

Беллоче

Müller

Menten

et al. 2013

A&A

385

523

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“…However, low-energy transitions of H 2 CO (e.g., 1 11 -1 10 ) in TMC-1 have been observed to exhibit absorption against the cosmic background (Palmer et al 1969). It is also noteworthy that the GBT detection of ketenimine (CH 2 CNH; Lovas et al 2006) in absorption toward Sgr B2(N-LMH) suggests that an intermediate-temperature region is responsible because the transitions involved are between intermediate-energy levels that range from 33 to 51 K.As a consequence of our deep integration observations in search of new molecules, extensive low noise level data have been collected in 85 spectrometer bandpasses centered at different frequencies in the range of 1-48 GHz. The continuum antenna temperature in each spectrometer bandpass is observed to be a function of bandpass center frequency, thus providing the means for analyzing the source of continuum reported here.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Nonthermal Continuum toward Sagittarius B2(N-LMH)

Hollis¹,

Jewell²,

Remijan³

et al. 2007

ApJ

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An analysis of continuum antenna temperatures observed in the GBT spectrometer bandpasses is presented for observations toward Sgr B2(N-LMH). Since 2004, we have identified four new prebiotic molecules toward this source by means of rotational transitions between low-energy levels; concurrently, we have observed significant continuum in GBT spectrometer bandpasses centered at 85 different frequencies in the range 1-48 GHz. The continuum heavily influences the molecular spectral features since we have observed far more absorption lines than emission lines for each of these new molecular species. Hence, it is important to understand the nature, distribution, and intensity of the underlying continuum in the GBT bandpasses for the purposes of radiative transfer, i.e., the means by which reliable molecular abundances are estimated. We find that the GBT spectrometer bandpass continuum is consistent with optically thin, nonthermal (synchrotron) emission with a flux density spectral index of Ϫ0.7 and a Gaussian source size of ∼143Љ at 1 GHz that decreases with increasing frequency as . Some support for this model is provided by high-frequency VLA observations of Sgr B2. The north source in Sgr B2, i.e., Sgr B2(N), is a giant star-forming region that lies along the Galactic equator near the center of our Galaxy. There is another strong molecular source ∼60Љ to the south of this position known as the main in Sgr B2, i.e., Sgr B2(M), that can influence molecular detections toward Sgr B2(N) if the telescope beam is large. Both Sgr B2(N) and Sgr B2(M) contain molecular maser-emitting spots, ultracompact H ii continuum sources, compact hot molecular cores of arcsecond dimensions, extended H ii regions, and cold extended molecular regions of arcminute dimensions. In addition, small-scale and large-scale shock phenomena pervade this region (e.g., Chengalur & Kanekar 2003). In Sgr B2(N), the hot molecular core known as the LMH (Large Molecule Heimat) has been a primary source that has been searched for millimeter-wave rotational transitions between high-energy levels for species that are found in emission and confined to its ∼5Љ diameter. For example, from interferometric observations, the emission from high-energy transitions of methyl formate (CH 3 OCHO; Snyder et al. 2002) is seen largely confined to the LMH core. High-energy transitions of methanol (CH 3 OH) are also confined to the LMH hot core, and they were used by Pei et al. (2000) to derive a rotational temperature of K that is usually assumed to characterize other large 170 ‫ע‬ 13 molecules in the core.On the other hand, recent observations with the Green Bank Telescope (GBT) toward Sgr B2(N-LMH) indicate that the molecular halo surrounding the LMH is a rich source of an entirely different set of large complex molecules. In this cold halo region, transitions between low-energy levels of large interstellar molecules tend to occur in the frequency range 1-48 GHz. For example, glycolaldehyde (CH 2 OHCHO) was first detected in this region with the GBT by means o...

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“…It was firstly synthesized by Staudinger and Hauser in 1919 [61]; it has been assigned as one of the chemical components of the interstellar medium [62] and its spectrum has been obtained [63][64][65][66][67][68][69][70]. Moreover, theoretical studies to obtain the optimized geometries of ketenimines and the substituent effects on the stability of ketenimines have been reported [71][72][73][74][75][76][77][78][79][80].…”

Section: Introductionmentioning

confidence: 99%

Computational study for the second-stage cracking of the pyrolysis of ethylamine: Decomposition of methanimine, ethenamine, and ethanimine

Almatarneh

Barhoumi

Al-Tayyem

et al. 2016

Computational and Theoretical Chemistry

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Accepted ManuscriptThis is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractThe mechanism that accounts for the observed experimental activation energy for the decomposition of ethylamine (EA) is still unknown. This paper reports the first detailed study of possible mechanisms for the pyrolysis of second-stage cracking product of ethylamine: the decomposition reaction of methanimine, ethanimine, and aminoethylene. Investigated reactions charactarise either H 2 elimination or 1,3-proton shift. These pathways result in the removal of H 2 , CH 4 , and NH 3 ; and the formation of hydrogen cyanide, acetylene, acetonitrile, ethynamine, and ketenimine. The IRC analysis was carried out for all transition state structures to obtain the complete reaction pathways. The stationary points were fully optimized at B3LYP and MP2 levels of theory using the 6-31G(d), 6-31G(2df,p), and 6-31++G(3df,3dp) basis sets. Based on comparing energetic requirements, we find 1,3-proton shift is the most probable pathway for the decomposition of ethanimine. The decomposition reaction of ethenamine was the most plausible reaction with an activation energy of 297 kJ mol −1 calculated at the composite method of G4MP2.

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Detection of Ketenimine (CH ₂ CNH) in Sagittarius B2(N) Hot Cores

Cited by 91 publications

References 18 publications

Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)

Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)

Nonthermal Continuum toward Sagittarius B2(N-LMH)

Computational study for the second-stage cracking of the pyrolysis of ethylamine: Decomposition of methanimine, ethenamine, and ethanimine

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Detection of Ketenimine (CH 2 CNH) in Sagittarius B2(N) Hot Cores

Cited by 91 publications

References 18 publications

Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)

Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)

Nonthermal Continuum toward Sagittarius B2(N-LMH)

Computational study for the second-stage cracking of the pyrolysis of ethylamine: Decomposition of methanimine, ethenamine, and ethanimine

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Product

Resources

About

Detection of Ketenimine (CH ₂ CNH) in Sagittarius B2(N) Hot Cores