Laboratory and astronomical detection of the cyclic C3H radical

Yamamoto, Satoshi; Saito, Shuji; Ohishi, Masatoshi; Suzuki, Hiroko; Ishikawa, Shinya; Kaifu, Norio; Murakami, Akinori

doi:10.1086/185036

Cited by 132 publications

(61 citation statements)

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“…(1) Woon (1995); (2) The dipole moment is assumed to be the same as for the C 2 H; (3) Pety et al (2012); (4) Yamamoto et al (1987b); (5) Kanata et al (1987); (6) DeFrees & McLean (1986).…”

Section: Hmentioning

confidence: 99%

“…The C 3 H radical is found in the ISM in two isomeric forms: as a linear chain, l-C 3 H, and as a three-carbon ring, c-C 3 H. Both isomers were first detected by their rotational transitions at millimetre wavelengths in TMC-1 (Thaddeus et al 1985a;Yamamoto et al 1987b). The c-C 3 H radical is more energetically stable than l-C 3 H by ∼860 K (Sheehan et al 2008).…”

Section: Hmentioning

confidence: 99%

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The chemistry and spatial distribution of small hydrocarbons in UV-irradiated molecular clouds: the Orion Bar PDR

Cuadrado

Goicoechea

Pilleri

et al. 2015

A&A

122

177

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Context. Carbon chemistry plays a pivotal role in the interstellar medium (ISM) but even the synthesis of the simplest hydrocarbons and how they relate to polycyclic aromatic hydrocarbons (PAHs) and grains is not well understood. Aims. We study the spatial distribution and chemistry of small hydrocarbons in the Orion Bar photodissociation region (PDR), a prototypical environment in which to investigate molecular gas irradiated by strong UV fields. Methods. We used the IRAM 30 m telescope to carry out a millimetre line survey towards the Orion Bar edge, complemented with ∼2 × 2 maps of the C 2 H and c-C 3 H 2 emission. We analyse the excitation of the detected hydrocarbons and constrain the physical conditions of the emitting regions with non-LTE radiative transfer models. We compare the inferred column densities with updated gas-phase photochemical models including 13 CCH and C 13 CH isotopomer fractionation.Results. Approximately 40% of the lines in the survey arise from hydrocarbons (C 2 H, C 4 H, c-C 3 H 2 , c-C 3 H, C 13 CH, 13 CCH, l-C 3 H, and l-H 2 C 3 in decreasing order of abundance). We detect new lines from l-C 3 H + and improve its rotational spectroscopic constants. Anions or deuterated hydrocarbons are not detected, but we provide accurate upper limit abundances:Conclusions. Our models can reasonably match the observed column densities of most hydrocarbons (within factors of <3). Since the observed spatial distribution of the C 2 H and c-C 3 H 2 emission is similar but does not follow the PAH emission, we conclude that, in high UV-flux PDRs, photodestruction of PAHs is not a necessary requirement to explain the observed abundances of the smallest hydrocarbons. Instead, gas-phase endothermic reactions (or with barriers) between C + , radicals, and H 2 enhance the formation of simple hydrocarbons. Observations and models suggest that the [C 2 H]/[c-C 3 H 2 ] ratio (∼32 at the PDR edge) decreases with the UV field attenuation. The observed low cyclic-to-linear C 3 H column density ratio (≤3) is consistent with a high electron abundance (x e ) PDR environment. In fact, the poorly constrained x e gradient influences much of the hydrocarbon chemistry in the more UV-shielded gas. The inferred hot rotational temperatures for C 4 H and l-C 3 H + also suggest that radiative IR pumping affects their excitation. We propose that reactions of C 2 H isotopologues with 13 C + and H atoms can explain the observed [C 13 CH]/[ 13 CCH] = 1.4 ± 0.1 fractionation level.

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“…(1) Woon (1995); (2) The dipole moment is assumed to be the same as for the C 2 H; (3) Pety et al (2012); (4) Yamamoto et al (1987b); (5) Kanata et al (1987); (6) DeFrees & McLean (1986).…”

Section: Hmentioning

confidence: 99%

Section: Hmentioning

confidence: 99%

The chemistry and spatial distribution of small hydrocarbons in UV-irradiated molecular clouds: the Orion Bar PDR

Cuadrado

Goicoechea

Pilleri

et al. 2015

A&A

122

177

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“…As stated previously, we have decided, for simplicity, to refer to species that contain such unsaturated polycarbon chains as cumulenes, or later as heterocumulenes; even though this nomenclature may not be strictly correct in each case. It is signi®cant to note that for some of these cumulenes there exist structural isomers as in the cases of C 3 H and C 3 H 2 , where linear and cyclic isomers have both been detected (Yamamoto et al, 1987;Thaddeus et al, 1993). Along with the unsaturated hydrocarbons, many species that include heteroatoms in the carbon chain, such as C n O, HC n O, C n N, HC n N, C n S, and C n Si, have also been detected.…”

Section: A Detection Of Molecules In Interstellar and Circumstellar mentioning

confidence: 99%

Construction of interstellar cumulenes and heterocumulenes: Mass Spectrometric Studies

Blanksby

Bowie

1999

Mass Spectrom. Rev.

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“…In this context we note, that the radiative lifetime of the 1 10 level is larger than that of all other levels by more than one order of magnitude (see Tables 1 and 2). Figure 4 shows the results for the 2 12 → 1 11 transition at 91.5 GHz, which was observed by Yamamoto et al (1987) in TMC-1 and searched for in the direction of Cas A. At this high frequency, the non-thermal background is very low and therefore has only little effect on the appearance of the line.…”

Section: The C-c 3 H Radicalmentioning

confidence: 84%

“…It was first detected by Yamamoto et al (1987) in TMC-1, who observed the 2 12 → 1 11 transition at 91.5 GHz in emission. Later, Mangum & Wootten (1990) observed the transition 1 10 → 1 11 at 14.8 GHz in emission in 12 additional galactic objects.…”

Section: Introductionmentioning

confidence: 89%

Anomalous absorption in c-C₃H and c-C₃D radicals

Chandra

Shinde

Kegel

et al. 2007

A&A

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Context. The c-C 3 H radical was first detected in TMC-1 by Yamamoto et al. (1987, ApJ, 322, L55), who observed the 2 12 → 1 11 transition at 91.5 GHz in emission. Mangum & Wootten (1990, A&A, 239, 319) observed the 1 10 → 1 11 transition at 14.8 GHz in emission in 12 additional galactic objects. Aims. The aim of this investigation is a quantitative estimate of relative line intensities under NLTE conditions. Methods. For wide ranges of physical parameters, where these molecules may be found, we have solved a set of statistical equilibrium equations coupled with the equations of radiative transfer in an on-the-spot approximation. For c-C 3 H, we accounted for 51 energy levels connected by 207 radiative transitions, and for c-C 3 D, we accounted for 51 energy levels connected by 205 radiative transitions. Results. Our results show that the 3 31 → 3 30 transition of c-C 3 H and c-C 3 D may be found in absorption against the cosmic microwave background (CMB). Furthermore, we found population inversion for the 1 10 → 1 11 transition. These findings may be useful in identifying these molecules in other cosmic objects, as well as for the determination of physical parameters in these objects.

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Laboratory and astronomical detection of the cyclic C3H radical

Cited by 132 publications

References 0 publications

The chemistry and spatial distribution of small hydrocarbons in UV-irradiated molecular clouds: the Orion Bar PDR

The chemistry and spatial distribution of small hydrocarbons in UV-irradiated molecular clouds: the Orion Bar PDR

Construction of interstellar cumulenes and heterocumulenes: Mass Spectrometric Studies

Anomalous absorption in c-C₃H and c-C₃D radicals

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Laboratory and astronomical detection of the cyclic C3H radical

Cited by 132 publications

References 0 publications

The chemistry and spatial distribution of small hydrocarbons in UV-irradiated molecular clouds: the Orion Bar PDR

The chemistry and spatial distribution of small hydrocarbons in UV-irradiated molecular clouds: the Orion Bar PDR

Construction of interstellar cumulenes and heterocumulenes: Mass Spectrometric Studies

Anomalous absorption in c-C3H and c-C3D radicals

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Anomalous absorption in c-C₃H and c-C₃D radicals