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| molecules:ism:fullerene [2019/02/25 22:38] – external edit 127.0.0.1 | molecules:ism:fullerene [2019/10/24 10:04] (current) – mueller |
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| ==== C60 ==== | ==== C60 ==== |
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| Fullerenes, and in particular the most stable small fullerene C<sub>60</sub>, were sought for quite extensively. Initially, they appeared to be rather elusive. Shortly after the definitive detection of C<sub>60</sub> and C<sub>70</sub>, described below in the [[http://www.astro.uni-koeln.de/site/vorhersagen/molecules/ism/Fullerene.html#C70|C<sub>70</sub> subsection]], they appeared to be almost ubiquitous as described below and in the Extragalactic section. However, a very recent laboratory spectroscopic investigation by\\ | Fullerenes, and in particular the most stable small fullerene C<sub>60</sub>, were sought for quite extensively. Initially, they appeared to be rather elusive. Shortly after the definitive detection of C<sub>60</sub> and C<sub>70</sub>, described below in the [[molecules:ism:fullerene#c70|C<sub>70</sub> subsection]], they appeared to be almost ubiquitous as described below and in the Extragalactic section. However, a very recent laboratory spectroscopic investigation by\\ |
| W. W. Duley and A. Hu,\\ | W. W. Duley and A. Hu,\\ |
| **[[http://dx.doi.org/10.1088/2041-8205/745/1/L11|Fullerenes and Proto-fullerenes in Interstellar Carbon Dust]]**,\\ | **[[https://doi.org/10.1088/2041-8205/745/1/L11|Fullerenes and Proto-fullerenes in Interstellar Carbon Dust]]**,\\ |
| //Astrophys. J.// **659**, Art. No. L11 (2012);\\ | //Astrophys. J.// **659**, Art. No. L11 (2012);\\ |
| concluded that the presence of PAH molecules and of fullerenes are mutually exclusive. In fact, the dehydrogenation of PAHs involves pseudo-fullerenes which still contain H atoms and which are not as symmetric as C<sub>60</sub>. Prior to turning to fullerenes, these molecules exhibit IR bands similar to C<sub>60</sub>, but in addition a strong mode near 16.4 μm (610 cm<sup>–1</sup>). The IR bands of fullerenes are apparently less specific than had been thought. This fact, however, had been known for the mid-infrared features of PAHs for a long time. As a consequence, the authors cast doubt on all reported detections of C<sub>60</sub> described in this section and in the Extragalactic section. The only uncontested report appears to be the one in which C<sub>60</sub> and C<sub>70</sub> were detected in Tc 1, see below. | concluded that the presence of PAH molecules and of fullerenes are mutually exclusive. In fact, the dehydrogenation of PAHs involves pseudo-fullerenes which still contain H atoms and which are not as symmetric as C<sub>60</sub>. Prior to turning to fullerenes, these molecules exhibit IR bands similar to C<sub>60</sub>, but in addition a strong mode near 16.4 μm (610 cm<sup>–1</sup>). The IR bands of fullerenes are apparently less specific than had been thought. This fact, however, had been known for the mid-infrared features of PAHs for a long time. As a consequence, the authors cast doubt on all reported detections of C<sub>60</sub> described in this section and in the Extragalactic section. The only uncontested report appears to be the one in which C<sub>60</sub> and C<sub>70</sub> were detected in Tc 1, see below. |
| Probably the first, tentative report, which seemed to be substantiated later, was published by\\ | Probably the first, tentative report, which seemed to be substantiated later, was published by\\ |
| M. W. Werner, K. I. Uchida, K. Sellgren, M. Marengo, K. D. Gordon, P. W. Morris, J. R. Houck, and J. A. Stansberry,\\ | M. W. Werner, K. I. Uchida, K. Sellgren, M. Marengo, K. D. Gordon, P. W. Morris, J. R. Houck, and J. A. Stansberry,\\ |
| **[[http://dx.doi.org/10.1086/422413|New Infrared Emission Features and Spectral Variations in NGC 7023]]**,\\ | **[[https://doi.org/10.1086/422413|New Infrared Emission Features and Spectral Variations in NGC 7023]]**,\\ |
| //Astrophys. J. Suppl. Ser.// **154**, 309–314 (2004).\\ | //Astrophys. J. Suppl. Ser.// **154**, 309–314 (2004).\\ |
| The reflection nebula was studied with //Spitzer//. In a note added in proof, they mentioned that M. Jura of UCLA pointed out that features at 17.4 and about 19.0 μm may be assigned to C<sub>60</sub>.\\ | The reflection nebula was studied with //Spitzer//. In a note added in proof, they mentioned that M. Jura of UCLA pointed out that features at 17.4 and about 19.0 μm may be assigned to C<sub>60</sub>.\\ |
| A more recent and more detailed account by\\ | A more recent and more detailed account by\\ |
| K. Sellgren, K. I. Uchida, and M. W. Werner,\\ | K. Sellgren, K. I. Uchida, and M. W. Werner,\\ |
| **[[http://dx.doi.org/10.1086/511805|The 15–20 μm //Spitzer// Spectra of Interstellar Emission Features in NGC 7023]]**,\\ | **[[https://doi.org/10.1086/511805|The 15–20 μm //Spitzer// Spectra of Interstellar Emission Features in NGC 7023]]**,\\ |
| //Astrophys. J.// **659**, 1338–1351 (2007)\\ | //Astrophys. J.// **659**, 1338–1351 (2007)\\ |
| concluded that if the two modes are due to C<sub>60</sub>, then the 17.4 μm band is overlapped in certain spatial regions.\\ | concluded that if the two modes are due to C<sub>60</sub>, then the 17.4 μm band is overlapped in certain spatial regions.\\ |
| An even more recent paper by\\ | An even more recent paper by\\ |
| K. Sellgren, M. W. Werner, J. G. Ingalls, J. D. T. Smith, T. M. Carleton, and C. Joblin,\\ | K. Sellgren, M. W. Werner, J. G. Ingalls, J. D. T. Smith, T. M. Carleton, and C. Joblin,\\ |
| **[[http://dx.doi.org/10.1088/2041-8205/722/1/L54|C<sub>60</sub> in Reflection Nebulae]]**,\\ | **[[https://doi.org/10.1088/2041-8205/722/1/L54|C<sub>60</sub> in Reflection Nebulae]]**,\\ |
| //Astrophys. J.// **722**, L54–L57 (2010)\\ | //Astrophys. J.// **722**, L54–L57 (2010)\\ |
| emphasizes that C<sub>60</sub> should be present not only in NGC 7023, but also NGC 2023 because in addition to the two bands described above, a third of four fundamental vibrations seem to have been observed near 7.0 μm. The remaining band at 8.5 μm is strongly overlapped. The authors estimate that between 0.1 and 0.6 % of the interstellar carbon is locked up in C<sub>60</sub>. | emphasizes that C<sub>60</sub> should be present not only in NGC 7023, but also NGC 2023 because in addition to the two bands described above, a third of four fundamental vibrations seem to have been observed near 7.0 μm. The remaining band at 8.5 μm is strongly overlapped. The authors estimate that between 0.1 and 0.6 % of the interstellar carbon is locked up in C<sub>60</sub>. |
| Three out of the four fundamental modes of C<sub>60</sub> have reportedly been identified toward a star in the transition state from AGB star to planetary nebula by\\ | Three out of the four fundamental modes of C<sub>60</sub> have reportedly been identified toward a star in the transition state from AGB star to planetary nebula by\\ |
| Y. Zhang and S. Kwok,\\ | Y. Zhang and S. Kwok,\\ |
| **[[http://dx.doi.org/10.1088/0004-637X/730/2/126|Detection of C<sub>60</sub> in the Protoplanetary Nebula IRAS 01005+7910]]**,\\ | **[[https://doi.org/10.1088/0004-637X/730/2/126|Detection of C<sub>60</sub> in the Protoplanetary Nebula IRAS 01005+7910]]**,\\ |
| //Astrophys. J.// **730**, Art. No. 126 (2011). | //Astrophys. J.// **730**, Art. No. 126 (2011). |
| |
| C<sub>60</sub> was suggested to be present in R Coronae Borealis (RCB) stars, which are very hydrogen-poor, but rich in He and C. In fact, it was found only in DY Cen and possibly V854 Cen, two comparatively H-rich RCB stars, by\\ | C<sub>60</sub> was suggested to be present in R Coronae Borealis (RCB) stars, which are very hydrogen-poor, but rich in He and C. In fact, it was found only in DY Cen and possibly V854 Cen, two comparatively H-rich RCB stars, by\\ |
| D. A. García-Hernández, N. Kameswara Rao, D. L.Lambert,\\ | D. A. García-Hernández, N. Kameswara Rao, D. L.Lambert,\\ |
| **[[http://dx.doi.org/10.1088/0004-637X/729/2/126|Are C<sub>60</sub> Molecules Detectable in Circumstellar Shells of R Coronae Borealis Stars?]]**,\\ | **[[https://doi.org/10.1088/0004-637X/729/2/126|Are C<sub>60</sub> Molecules Detectable in Circumstellar Shells of R Coronae Borealis Stars?]]**,\\ |
| //Astrophys. J.// **729**, Art. No. 126 (2011). | //Astrophys. J.// **729**, Art. No. 126 (2011). |
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| J. Cami, J. Bernard-Salas, E. Peeters, and S. E. Malek,\\ | J. Cami, J. Bernard-Salas, E. Peeters, and S. E. Malek,\\ |
| reported on **[[http://dx.doi.org/10.1126/science.1192035|Detection of C<sub>60</sub> and C<sub>70</sub> in a Young Planetary Nebula]]**,\\ | reported on\\ |
| | **[[https://doi.org/10.1126/science.1192035|Detection of C<sub>60</sub> and C<sub>70</sub> in a Young Planetary Nebula]]**,\\ |
| //Science// **659**, 1180–1182 (2010).\\ | //Science// **659**, 1180–1182 (2010).\\ |
| They have used archival //Spitzer// data of Tc 1. The C<sub>60</sub> features at 17.4 and 18.9 μm overlap with slightly weaker C<sub>70</sub> features at similar positions. The 8.5 μm feature of C<sub>60</sub> was also observed, the one near 7.0 μm is overlapped by a much stronger Ar<sup>+</sup> line. Weak C<sub>70</sub> features at 12.5, 14.8, 15.6, and 21.8 μm seem to be free from overlap.\\ | They have used archival //Spitzer// data of Tc 1. The C<sub>60</sub> features at 17.4 and 18.9 μm overlap with slightly weaker C<sub>70</sub> features at similar positions. The 8.5 μm feature of C<sub>60</sub> was also observed, the one near 7.0 μm is overlapped by a much stronger Ar<sup>+</sup> line. Weak C<sub>70</sub> features at 12.5, 14.8, 15.6, and 21.8 μm seem to be free from overlap.\\ |