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molecules:ism:glycolaldehyd [2019/04/26 15:39] – mueller | molecules:ism:glycolaldehyd [2021/06/02 14:36] (current) – mueller | ||
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6 //b//-type rotational transitions in the 70 to 105 GHz region were searched for with the NRAO 12 m radio telescope in the former work. Two transitions were severely blended, the remaining four appeared to be free of contamination. No rotational temeperature was derived, but 200 K were assumed. Because of the small number of lines and possible line overlap this detection had to be viewed with some caution until further observations.\\ | 6 //b//-type rotational transitions in the 70 to 105 GHz region were searched for with the NRAO 12 m radio telescope in the former work. Two transitions were severely blended, the remaining four appeared to be free of contamination. No rotational temeperature was derived, but 200 K were assumed. Because of the small number of lines and possible line overlap this detection had to be viewed with some caution until further observations.\\ | ||
- | The 8< | + | The 8< |
A report on interstellar glycolaldehyde had been presented at the 58th International Symposium on Molecular Spectroscopy; | A report on interstellar glycolaldehyde had been presented at the 58th International Symposium on Molecular Spectroscopy; | ||
D. T. Halfen, A. J. Apponi, and L. M. Ziurys,\\ | D. T. Halfen, A. J. Apponi, and L. M. Ziurys,\\ | ||
**[[http:// | **[[http:// | ||
- | This contribution appeared to question the detection. | + | This contribution appeared to question the detection.\\ |
Recent observations of the four lowest //< | Recent observations of the four lowest //< | ||
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**[[https:// | **[[https:// | ||
// | // | ||
- | Interestingly, | + | Interestingly, |
The observations from the Ziurys group have appeared eventually: | The observations from the Ziurys group have appeared eventually: | ||
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Even though the article mentioned above already has secured the glycolaldehyde detection, this work is still worth mentioning because it shows how difficult it is to obtain definitive results for a moderately complex molecule. 40 (!) transitions have been searched for in the upper 4 mm region to the 2 mm region (68–169 GHz). No significant signals were detected for only two transitions which are fairly high in // | Even though the article mentioned above already has secured the glycolaldehyde detection, this work is still worth mentioning because it shows how difficult it is to obtain definitive results for a moderately complex molecule. 40 (!) transitions have been searched for in the upper 4 mm region to the 2 mm region (68–169 GHz). No significant signals were detected for only two transitions which are fairly high in // | ||
The rotational temperature derived from " | The rotational temperature derived from " | ||
- | Some of the observed U-lines may be caused by presently not identified species. However, a considerable number of these U-lines are caused most definitively by known species in higher rotationally or vibrationally excited states or by minor isotopic species. It is also obvious that the unambiguous identification of molecules more complex than glycolaldehyde will be even more challenging. | + | Some of the observed U-lines may be caused by presently not identified species. However, a considerable number of these U-lines are caused most definitively by known species in higher rotationally or vibrationally excited states or by minor isotopic species. It is also obvious that the unambiguous identification of molecules more complex than glycolaldehyde will be even more challenging.\\ |
The molecule was also detected in three Galactic center molecular clouds which have low dust temperatures (10–20 K), | The molecule was also detected in three Galactic center molecular clouds which have low dust temperatures (10–20 K), | ||
M. A. Requena-Torres, | M. A. Requena-Torres, | ||
**[[https:// | **[[https:// | ||
- | // | + | // |
A report on the\\ | A report on the\\ | ||
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by M. T. Beltrán, C. Codella, S. Viti, R. Neri, and R. Cesaroni,\\ | by M. T. Beltrán, C. Codella, S. Viti, R. Neri, and R. Cesaroni,\\ | ||
// | // | ||
- | with the IRAM Plateau de Bure Interferometer toward the high mass star-forming region G31.41+0.31 should be viewed with great caution because only three transitions were searched for (near 220.5, 143.6 and 103.7 GHz), | + | with the IRAM Plateau de Bure Interferometer toward the high mass star-forming region G31.41+0.31 should be viewed with great caution because only three transitions were searched for (near 220.5, 143.6 and 103.7 GHz), |
The situation is more favorable in\\ | The situation is more favorable in\\ | ||
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by J. K. Jørgensen, C. Favre, S. E. Bisschop, T. L. Bourke, E. F. van Dishoeck, and Markus Schmalzl,\\ | by J. K. Jørgensen, C. Favre, S. E. Bisschop, T. L. Bourke, E. F. van Dishoeck, and Markus Schmalzl,\\ | ||
// | // | ||
- | 6 emission features were observed in a small frequency region near 200 GHz toward source B of IRAS 16293-2422. Though two of the featueres are very weak and at least two are blended, the situation is much more favorable than the one described in the previous paragraph – even if one takes into account that several other features remained unassigned. A rotational temperature of about 300 K was estimated for glycolaldehyde as well as for its isomer methyl formate, which has a column density slightly more than one order of magnitude higher than that of glycolaldehyde. The two molecules were also seen toward source A with similar column densities as in source B, but with a rotational temperature estimated at about 200 K. Moreover, several additional features were seen near 700 GHz red-shifted and in absorption toward source B; slightly off source, the same lines were seen unshifted in emission. This was interpreted as a sign of infall. | + | 6 emission features were observed in a small frequency region near 200 GHz toward source B of IRAS 16293-2422. Though two of the featueres are very weak and at least two are blended, the situation is much more favorable than the one described in the previous paragraph – even if one takes into account that several other features remained unassigned. A rotational temperature of about 300 K was estimated for glycolaldehyde as well as for its isomer methyl formate, which has a column density slightly more than one order of magnitude higher than that of glycolaldehyde. The two molecules were also seen toward source A with similar column densities as in source B, but with a rotational temperature estimated at about 200 K. Moreover, several additional features were seen near 700 GHz red-shifted and in absorption toward source B; slightly off source, the same lines were seen unshifted in emission. This was interpreted as a sign of infall.\\ |
+ | This work also reports the identification of three lines attributed to // | ||
J. K. Jørgensen, M. H. D. van der Wiel, A. Coutens, J. M. Lykke, H. S. P. Müller, E. F. van Dishoeck, H. Calcutt, P. Bjerkeli, T. L. Bourke, M. N. Drozdovskaya, | J. K. Jørgensen, M. H. D. van der Wiel, A. Coutens, J. M. Lykke, H. S. P. Müller, E. F. van Dishoeck, H. Calcutt, P. Bjerkeli, T. L. Bourke, M. N. Drozdovskaya, | ||
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- | Contributor(s): | + | Contributor(s): |
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