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| molecules:extragalactic:fullerene_extragalactic [2019/02/25 22:38] – external edit 127.0.0.1 | molecules:extragalactic:fullerene_extragalactic [2019/10/22 16:32] (current) – [C60] mueller |
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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 Galactic detection of C<sub>60</sub> and C<sub>70</sub>, they appeared to be almost ubiquitous. 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 Galactic detection of C<sub>60</sub> and C<sub>70</sub>, they appeared to be almost ubiquitous. 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>). Some of 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 autors 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 in the Galactic section. However, some of the other detection are probably likely correct, even if some caution is advised. | 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>). Some of 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 autors 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 in the Galactic section. However, some of the other detection are probably likely correct, even if some caution is advised. |
| D. A. García-Hernández, A. Manchado, P. García-Lario, L. Stanghellini, E. Villaver, R. A. Shaw, R. Szczerba, and J. V. Perea-Calderón,\\ | D. A. García-Hernández, A. Manchado, P. García-Lario, L. Stanghellini, E. Villaver, R. A. Shaw, R. Szczerba, and J. V. Perea-Calderón,\\ |
| studied with //Spitzer//\\ | studied with //Spitzer//\\ |
| **[[http://dx.doi.org/10.1088/2041-8205/724/1/L39|Formation of Fullerenes in H-containing Planetary Nebulae]]**,\\ | **[[https://doi.org/10.1088/2041-8205/724/1/L39|Formation of Fullerenes in H-containing Planetary Nebulae]]**,\\ |
| //Astrophys. J.// **724**, Art. No. L39 (2010).\\ | //Astrophys. J.// **724**, Art. No. L39 (2010).\\ |
| Besides several Galactic sources, they also studied LHA 115-N 42, also known as SMP SMC 16, in the Small Magellanic Cloud. Strong features attributed to C<sub>60</sub> were detected near 17.4 and 18.9 μm. These features overlap with weaker features of C<sub>70</sub> in the Galactic PN Tc 1. However, a C<sub>70</sub> feature near 14.8 μm is clearly absent. The 8.5 μm feature of C<sub>60</sub> was also observed weakly, the one near 7.0 μm is overlapped by a much stronger Ar<sup>+</sup> line – similar to the situation in Tc 1. Because of the investigation mentioned above, this identification should be viewed with caution, though it appears to be rather likely. | Besides several Galactic sources, they also studied LHA 115-N 42, also known as SMP SMC 16, in the Small Magellanic Cloud. Strong features attributed to C<sub>60</sub> were detected near 17.4 and 18.9 μm. These features overlap with weaker features of C<sub>70</sub> in the Galactic PN Tc 1. However, a C<sub>70</sub> feature near 14.8 μm is clearly absent. The 8.5 μm feature of C<sub>60</sub> was also observed weakly, the one near 7.0 μm is overlapped by a much stronger Ar<sup>+</sup> line – similar to the situation in Tc 1. Because of the investigation mentioned above, this identification should be viewed with caution, though it appears to be rather likely. |