Accurate rest frequencies for the submillimetre-wave lines of the $^{15}{\bf N}$-containing
 isotopologues of $\bf N_{2}H^+$ and $\bf N_{2}D^+$

Dore, Luca; Bizzocchi, L.; Esposti, C. Degli; Tinti, Francesca

doi:10.1051/0004-6361/200811235

Cited by 23 publications

(27 citation statements)

References 19 publications

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“…The 14 N hyperfine splitting values were taken from Caselli et al (1995). Entries for the 15 N isotopologues were generated from results published by Dore et al (2009). The J = 1-0 transitions were taken from Gudeman (1982).…”

Section: Diazenylium N 2 H +mentioning

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

389

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: Diazenylium N 2 H +mentioning

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

389

523

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“…We therefore performed close-coupling calculations (Arthurs & Dalgarno 1960) for the pure rotational excitation cross-sections using the MOLSCAT program (Hutson & Green 1994), as in Lique et al (2015) for the main isotopolog. The N 15 NH + rotational energy levels were computed using the rotational constants of Dore et al (2009). Calculations were carried out for total energies of up to 500 cm −1 .…”

Section: N 2 H + and N 15 Nh + Collisional Rate Coefficientsmentioning

confidence: 99%

N₂H⁺and N¹⁵NH⁺toward the prestellar core 16293E in L1689N

Daniel

Fauré

Pagani

et al. 2016

A&A

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Context. Understanding the processes that could lead to an enrichment of molecules in 15 N atoms is of particular interest because this may shed light on the relatively strong variations observed in the 14 N/ 15 N ratio in various solar system environments. Aims. The sample of molecular clouds where 14 N/ 15 N ratios have been measured currently is small and has to be enlarged to allow statistically significant studies. In particular, the N 2 H + molecule currently shows the broadest spread of 14 N/ 15 N ratios in high-mass star-forming regions. However, the 14 N/ 15 N ratio in N 2 H + was obtained in only two low-mass star-forming regions (L1544 and B1b). We here extend this sample to a third dark cloud. Methods. We targeted the 16293E prestellar core, where the N 15 NH + J = 1−0 line was detected. Using a model previously developed for the physical structure of the source, we solved the molecular excitation with a nonlocal radiative transfer code. For this purpose, we computed specific collisional rate coefficients for the N 15 NH + -H 2 collisional system. As a first step of the analysis, the N 2 H + abundance profile was constrained by reproducing the N 2 H + J = 1−0 and 3−2 maps. A scaling factor was then applied to this profile to match the N 15 NH + J = 1−0 spectrum. Results. We derive a column density ratio N 2 H + /N 15 NH + = 330 +170 −100 . Conclusions. We performed a detailed analysis of the excitation of N 2 H + and N 15 NH + in the direction of the 16293E core with modern models that solve the radiative transfer and with the most accurate collisional rate coefficients available to date. We obtained the third estimate of the N 2 H + /N 15 NH + column density ratio in the direction of a cold prestellar core. The current estimate ∼330 agrees with the typical value of the elemental isotopic ratio in the local interstellar medium. It is lower than in some other cores, however, where values as high as 1300 have been reported.

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“…We calculated a full set of hyperfine de-excitation Dore et al (2009), whereas for the parent species they…”

Section: Appendix B: Rate Coefficient Tablesmentioning

confidence: 99%

Detection of¹⁵NNH⁺in L1544: non-LTE modelling of dyazenilium hyperfine line emission and accurate¹⁴N/¹⁵N values

Bizzocchi¹,

Caselli²,

Leonardo³

et al. 2013

A&A

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110

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Context. Samples of pristine solar system material found in meteorites and interplanetary dust particles are highly enriched in 15 N. Conspicuous nitrogen isotopic anomalies have also been measured in comets, and the 14 N/ 15 N abundance ratio of the Earth is itself higher than the recognised presolar value by almost a factor of two. Low-temperature ion/molecule reactions in the proto-solar nebula have been repeatedly indicated as being responsible for these 15 N-enhancements.

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Accurate rest frequencies for the submillimetre-wave lines of the $^{15}{\bf N}$-containing isotopologues of $\bf N_{2}H^+$ and $\bf N_{2}D^+$

Cited by 23 publications

References 19 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)

N₂H⁺and N¹⁵NH⁺toward the prestellar core 16293E in L1689N

Detection of¹⁵NNH⁺in L1544: non-LTE modelling of dyazenilium hyperfine line emission and accurate¹⁴N/¹⁵N values

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Accurate rest frequencies for the submillimetre-wave lines of the $^{15}{\bf N}$-containing isotopologues of $\bf N_{2}H^+$ and $\bf N_{2}D^+$

Cited by 23 publications

References 19 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)

N2H+and N15NH+toward the prestellar core 16293E in L1689N

Detection of15NNH+in L1544: non-LTE modelling of dyazenilium hyperfine line emission and accurate14N/15N values

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N₂H⁺and N¹⁵NH⁺toward the prestellar core 16293E in L1689N

Detection of¹⁵NNH⁺in L1544: non-LTE modelling of dyazenilium hyperfine line emission and accurate¹⁴N/¹⁵N values