M. Basire, P. Parneix, T. Pino, P. Bréchignac, F. Calvo
The IR emission cascade from the pyrene cation due to a broad band optical excitation is simulated using kinetic Monte Carlo. Anharmonicities of the ground electronic state potential energy surface are taken into account in the transition energies, the microcanonical densities of states, and the rate of hydrogen loss through various statistical theories. The emission spectral features of the “3.3”, “6.2” and “11.2” μ m bands are computed for different blackbody temperatures.
{"title":"Modeling the Anharmonic Infrared Emission Spectra of PAHs: Application to the Pyrene Cation","authors":"M. Basire, P. Parneix, T. Pino, P. Bréchignac, F. Calvo","doi":"10.1051/EAS/1146009","DOIUrl":"https://doi.org/10.1051/EAS/1146009","url":null,"abstract":"The IR emission cascade from the pyrene cation due to a broad band optical excitation is simulated using kinetic Monte Carlo. Anharmonicities of the ground electronic state potential energy surface are taken into account in the transition energies, the microcanonical densities of states, and the rate of hydrogen loss through various statistical theories. The emission spectral features of the “3.3”, “6.2” and “11.2” μ m bands are computed for different blackbody temperatures.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130127859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Hamberg, E. Vigren, R. Thomas, V. Zhaunerchyk, M. Zhang, S. Trippel, M. Kamińska, I. Kashperka, M. A. Ugglas, A. Källberg, A. Simonsson, A. Paál, J. Semaniak, M. Larsson, W. Geppert
We have investigated the dissociative recombination (DR) of the C 6 D 6 + and C 6 D 7 + ions using the CRYRING heavy-ion storage ring at Stockholm University, Sweden. The dissociative recombination branching ratios were determined at minimal collision energy, showing that the DR of both ions was dominated by pathways keeping the carbon atoms together in one product. The absolute reaction cross sections for the titular ions are best fitted by σ (E cm [eV]) = 1.3 ± 0.4 × 10 -15 (E cm [eV]) −1.19 ± 0.02 cm 2 (C 6 D 6 + ) and σ (E cm [eV]) = 1.1 ± 0.3 × 10 -15 (E cm [eV]) −1.33 ± 0.02 cm 2 (C 6 D 7 + ) in the intervals 3-300 meV and 3-200 meV respectively. The thermal rate constants of the titular reactions are best described by: k(T) = 1.3 ± 0.4 × 10 -6 (T/300) −0.69 ± 0.02 cm 3 s -1 for C 6 D 6 + and k(T) = 2.0 ± 0.6 × 10 -6 (T/300) −0.83 ± 0.02 cm 3 s -1 for C 6 D 7 + . These expressions correlates well with earlier flowing afterglow studies on the same process.
我们利用瑞典斯德哥尔摩大学的CRYRING重离子储存环研究了c6d6 +和c6d7 +离子的解离重组(DR)。在最小碰撞能量下确定了解离重组分支比，表明两个离子的DR主要是由保持碳原子在一个产物中在一起的途径决定的。在3 ~ 300 meV和3 ~ 200 meV范围内，分别用σ (E cm [eV]) = 1.3±0.4 × 10 -15 (E cm [eV]) - 1.19±0.02 cm 2 (c6d6 +)和σ (E cm [eV]) = 1.1±0.3 × 10 -15 (E cm [eV]) - 1.33±0.02 cm 2 (c6d7 +)来拟合名义离子的绝对反应截面。对于c6d6 +， k(T) = 1.3±0.4 × 10 -6 (T/300)−0.69±0.02 cm 3 s -1;对于c6d7 +， k(T) = 2.0±0.6 × 10 -6 (T/300)−0.83±0.02 cm 3 s -1。这些表达式与先前对同一过程的流动余辉的研究有很好的相关性。
{"title":"Experimental Studies of the Dissociative Recombination Processes for the C6D+\u0000 6 and C6D+\u0000 7 Ions","authors":"M. Hamberg, E. Vigren, R. Thomas, V. Zhaunerchyk, M. Zhang, S. Trippel, M. Kamińska, I. Kashperka, M. A. Ugglas, A. Källberg, A. Simonsson, A. Paál, J. Semaniak, M. Larsson, W. Geppert","doi":"10.1051/EAS/1146026","DOIUrl":"https://doi.org/10.1051/EAS/1146026","url":null,"abstract":"We have investigated the dissociative recombination (DR) of the\u0000 C 6 D 6 + and C 6 D 7 + ions using the CRYRING heavy-ion storage ring at Stockholm University, Sweden. The\u0000 dissociative recombination branching ratios were determined at minimal collision energy, showing that the DR of both ions was dominated by pathways keeping the carbon atoms\u0000 together in one product. The absolute reaction cross sections for the titular ions are\u0000 best fitted by σ (E cm [eV]) = 1.3 ± 0.4 × 10 -15 (E cm [eV]) −1.19 ± 0.02 cm 2 (C 6 D 6 + )\u0000 and σ (E cm [eV]) = 1.1 ± 0.3 × \u0000 10 -15 (E cm [eV]) −1.33 ± 0.02 cm 2 (C 6 D 7 + )\u0000 in the intervals 3-300 meV and 3-200 meV respectively. The thermal rate constants of the\u0000 titular reactions are best described by:\u0000 k(T) = 1.3 ± 0.4 × 10 -6 (T/300) −0.69 ± 0.02 cm 3 s -1 for C 6 D 6 + and k(T) = 2.0 ± 0.6 × 10 -6 (T/300) −0.83 ± 0.02 cm 3 s -1 for C 6 D 7 + .\u0000 These expressions correlates well with earlier flowing afterglow studies on the same\u0000 process.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"187 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122773365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The spectroscopic properties of protonated and deprotonated PAHs are investigated through Density Functional Theory (DFT) cal- culations, with reference to their potential astrophysical significance. Attention is focussed on electronic and rotational spectra.
{"title":"Spectroscopy of Protonated and Deprotonated PAHs","authors":"M. Hammonds, A. Candian","doi":"10.1051/EAS/1146038","DOIUrl":"https://doi.org/10.1051/EAS/1146038","url":null,"abstract":"The spectroscopic properties of protonated and deprotonated PAHs are investigated through Density Functional Theory (DFT) cal- culations, with reference to their potential astrophysical significance. Attention is focussed on electronic and rotational spectra.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129400766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper reviews the various processes that have been pro- posed to explain the observed trend of PAH strength with metallicity. It summarizes a study showing that, although PAH destruction by hard radiation is important in low-metallicity environments, it is not suffi- cient to explain their paucity. In these systems, the deficiency of their formation mechanism, related to stellar evolution, has to be invoked.
{"title":"Dialectics of the PAH Abundance Trend with Metallicity","authors":"F. Galliano","doi":"10.1051/EAS/1146004","DOIUrl":"https://doi.org/10.1051/EAS/1146004","url":null,"abstract":"This paper reviews the various processes that have been pro- posed to explain the observed trend of PAH strength with metallicity. It summarizes a study showing that, although PAH destruction by hard radiation is important in low-metallicity environments, it is not suffi- cient to explain their paucity. In these systems, the deficiency of their formation mechanism, related to stellar evolution, has to be invoked.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128429391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Bouwman, H. Cuppen, L. Allamandola, H. Linnartz
The mid-infrared emission of Polycyclic Aromatic Hydrocarbons is found in many phases of the interstellar medium. Towards cold dense clouds, however, the emission is heavily quenched. In these regions molecules are found to efficiently freeze-out on interstellar grains forming thin layers of ices. PAHs are highly non-volatile molecules and are also expected to freeze-out. PAHs trapped in interstellar ices are likely to participate in the overall chemistry, leading to the formation of cations and complex molecules in the solid-state. The work presented here aims to experimentally study the chemical reactions that PAHs undergo upon vacuum ultraviolet irradiation when trapped in interstellar H 2 O ice.
{"title":"VUV Photochemistry of PAHs Trapped in Interstellar Water Ice","authors":"J. Bouwman, H. Cuppen, L. Allamandola, H. Linnartz","doi":"10.1051/EAS/1146027","DOIUrl":"https://doi.org/10.1051/EAS/1146027","url":null,"abstract":"The mid-infrared emission of Polycyclic Aromatic Hydrocarbons is found in many phases of\u0000 the interstellar medium. Towards cold dense clouds, however, the emission is heavily\u0000 quenched. In these regions molecules are found to efficiently freeze-out on interstellar\u0000 grains forming thin layers of ices. PAHs are highly non-volatile molecules and are also\u0000 expected to freeze-out. PAHs trapped in interstellar ices are likely to participate in the\u0000 overall chemistry, leading to the formation of cations and complex molecules in the\u0000 solid-state. The work presented here aims to experimentally study the chemical reactions\u0000 that PAHs undergo upon vacuum ultraviolet irradiation when trapped in interstellar\u0000 H 2 O ice.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"83 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123674402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In dense molecular clouds, the birthplace of stars and planets, interstellar atoms and molecules freeze onto extremely cold dust and ice particles. These ices are processed by ultraviolet light and cosmic rays forming hundreds of far more complex species, some of astrobiological interest. Eventually, these rain down on primordial planets where they take part in the young chemistry on these new worlds. Although the IR spectroscopy and energetic processing of interstellar ice analogs have been studied for nearly 30 years, similar studies of PAH containing ices have only just begun. This paper presents recent results from laboratory studies on the vacuum ultraviolet (VUV) photochemistry of PAHs in water ice at low temperatures to assess the roles they play in the photochemical evolution of interstellar ices and their relevance to astrobiology. A number of “surprises” were found in these studies on PAH containing water-rich ices, indicating that PAHs likely play very important, unexpected roles in cosmic ice chemistry, physics and astrobiology.
{"title":"PAHs and Astrobiology","authors":"L. Allamandola","doi":"10.1051/EAS/1146032","DOIUrl":"https://doi.org/10.1051/EAS/1146032","url":null,"abstract":"In dense molecular clouds, the birthplace of stars and planets, interstellar atoms and molecules freeze onto extremely cold dust and ice particles. These ices are processed by ultraviolet light and cosmic rays forming hundreds of far more complex species, some of astrobiological interest. Eventually, these rain down on primordial planets where they take part in the young chemistry on these new worlds. Although the IR spectroscopy and energetic processing of interstellar ice analogs have been studied for nearly 30 years, similar studies of PAH containing ices have only just begun. This paper presents recent results from laboratory studies on the vacuum ultraviolet (VUV) photochemistry of PAHs in water ice at low temperatures to assess the roles they play in the photochemical evolution of interstellar ices and their relevance to astrobiology. A number of “surprises” were found in these studies on PAH containing water-rich ices, indicating that PAHs likely play very important, unexpected roles in cosmic ice chemistry, physics and astrobiology.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126174367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a Monte Carlo (MC) radiative transfer code for complex three dimensional dust distributions and include transiently heated PAH. The correctness of the code is confirmed by comparison with benchmark results. The method makes use of the parallelization capabilities of modern vectorized computing units like graphic cards. The computational speed grows linearly with the number of graphical processing units (GPU). On a conventional desktop PC, our code is up to a factor 100 faster when compared to other MC algorithms. As an example, we compute the dust emission of proto-planetary disks. We simulate how a mid-IR instrument mounted at a future 42 m ELT will detect such disks. Two cases are distinguished: a homogeneous disk and a disk with an outward migrating planet, producing a gap and a spiral density wave. We find that the resulting mid-IR spectra of both disks are almost identical. However, they can be distinguished at those wavelengths by coronographic, dual-band imaging. Finally, the emission of PAHs exposed to different radiation fields is computed. We demonstrate that PAH emission depends not only on the strength but also strongly on the hardness of the radiation, a fact which has often been neglected in previous models. We find that hard photons (>20 eV) easily dissociate all PAHs in the disks of T Tauri stars. To explain the low, but not negligible detection rate (<10%) of PAHs in T Tau disks, we suggest that turbulent motions act as a possible path for PAH survival.
{"title":"PAH in Vectorized Three Dimensional Monte Carlo Dust Radiative Transfer Models","authors":"R. Siebenmorgen, F. Heymann, E. Krügel","doi":"10.1051/EAS/1146030","DOIUrl":"https://doi.org/10.1051/EAS/1146030","url":null,"abstract":"We present a Monte Carlo (MC) radiative transfer code for complex three dimensional dust distributions and include transiently heated PAH. The correctness of the code is confirmed by comparison with benchmark results. The method makes use of the parallelization capabilities of modern vectorized computing units like graphic cards. The computational speed grows linearly with the number of graphical processing units (GPU). On a conventional desktop PC, our code is up to a factor 100 faster when compared to other MC algorithms. As an example, we compute the dust emission of proto-planetary disks. We simulate how a mid-IR instrument mounted at a future 42 m ELT will detect such disks. Two cases are distinguished: a homogeneous disk and a disk with an outward migrating planet, producing a gap and a spiral density wave. We find that the resulting mid-IR spectra of both disks are almost identical. However, they can be distinguished at those wavelengths by coronographic, dual-band imaging. Finally, the emission of PAHs exposed to different radiation fields is computed. We demonstrate that PAH emission depends not only on the strength but also strongly on the hardness of the radiation, a fact which has often been neglected in previous models. We find that hard photons (>20 eV) easily dissociate all PAHs in the disks of T Tauri stars. To explain the low, but not negligible detection rate (<10%) of PAHs in T Tau disks, we suggest that turbulent motions act as a possible path for PAH survival.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115240117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Physical dust models which include a PAH component are quite successful in reproducing the measured extinction vs. wavelength in the Milky Way, the infrared (IR) emission observed from Milky Way regions and other galaxies, and a number of other observational constraints. Many of the adopted PAH properties are necessarily highly idealized. The observed variations in the 7.7 μ m/11.3 μ m band ratio can be reproduced by varying the PAH ionization balance. Changing the spectrum of the starlight heating the PAHs affects the overall strength of the PAH emission (relative to total IR), but has relatively little effect on the 7.7 μ m/11.3 μ m band ratio.
{"title":"Astronomical Models of PAHs and Dust","authors":"B. Draine","doi":"10.1051/EAS/1146003","DOIUrl":"https://doi.org/10.1051/EAS/1146003","url":null,"abstract":"Physical dust models which include a PAH component are quite successful in reproducing the measured extinction vs. wavelength in the Milky Way, the infrared (IR) emission observed from Milky Way regions and other galaxies, and a number of other observational constraints. Many of the adopted PAH properties are necessarily highly idealized. The observed variations in the 7.7 μ m/11.3 μ m band ratio can be reproduced by varying the PAH ionization balance. Changing the spectrum of the starlight heating the PAHs affects the overall strength of the PAH emission (relative to total IR), but has relatively little effect on the 7.7 μ m/11.3 μ m band ratio.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134589306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Herschel opens the possibility to detect the low-frequency vibrational bands of individual polycyclic aromatic hydrocarbon (PAH) molecules and therefore to progress in our understanding of the nature of these species and the properties of the environments from which they emit. However, unless one individual molecule dominates the PAH family, this detection will not be straightforward and it is necessary to optimise the observational search with an educated guess of the band profiles and intensities. Such educated guess can be obtained from models that include a detailed description of the molecular properties (anharmonicity, rotation...) in the modelling of the cooling cascade of the emitting species. First results are expected soon from the observation of the Orion Bar as part of the HEXOS Herschel key program.
{"title":"Search for far-IR PAH Bands with Herschel: Modelling and Observational Approaches","authors":"C. Joblin, G. Mulas, G. Malloci, E. Bergin","doi":"10.1051/EAS/1146013","DOIUrl":"https://doi.org/10.1051/EAS/1146013","url":null,"abstract":"Herschel opens the possibility to detect the low-frequency vibrational bands of individual polycyclic aromatic hydrocarbon (PAH) molecules and therefore to progress in our understanding of the nature of these species and the properties of the environments from which they emit. However, unless one individual molecule dominates the PAH family, this detection will not be straightforward and it is necessary to optimise the observational search with an educated guess of the band profiles and intensities. Such educated guess can be obtained from models that include a detailed description of the molecular properties (anharmonicity, rotation...) in the modelling of the cooling cascade of the emitting species. First results are expected soon from the observation of the Orion Bar as part of the HEXOS Herschel key program.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132120935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A classical nova outburst arises from a thermonuclear run- away in the hydrogen-rich material accreted onto the surface of a white dwarf in a binary system. These explosions can produce copious amounts of heavy element enriched material that are ejected violently into the surrounding interstellar medium. In some novae, conditions in the ejecta are suitable for the formation of dust of various compositions, including silicates, amorphous carbon, silicon carbide, and hydrocar- bons. Multiple dust grain types are sometimes produced in the same system. CO formation in novae may not reach saturation, thus in- validating the usual paradigm in which the C:O ratio determines the dust species. A few novae, such as V705 Cas and DZ Cru, have ex- hibited emission features near 6, 8, and 11 µm that are similar to "Unidentified Infrared" (UIR) features, but with significant differences in position and band structure. Here, we present Spitzer IRS spectra of two recent dusty novae, V2361 Cyg and V2362 Cyg, that harbor similar peculiar emission structures superimposed on features arising from carbonaceous grains. In other astronomical objects, such as star forming regions and young stellar objects, emission peaks at 6.2, 7.7, and 11.3 µm have been associated with polycyclic aromatic hydro- carbon (PAH) complexes. We suggest that hydrogenated amorphous carbon (HAC) may be the source of these features in novae based upon the spectral behavior of the emission features and the conditions under which the dust formed.
{"title":"Atypical Dust Species in the Ejecta of Classical Novae","authors":"L. Helton, A. Evans, C. Woodward, R. Gehrz","doi":"10.1051/EAS/1146042","DOIUrl":"https://doi.org/10.1051/EAS/1146042","url":null,"abstract":"A classical nova outburst arises from a thermonuclear run- away in the hydrogen-rich material accreted onto the surface of a white dwarf in a binary system. These explosions can produce copious amounts of heavy element enriched material that are ejected violently into the surrounding interstellar medium. In some novae, conditions in the ejecta are suitable for the formation of dust of various compositions, including silicates, amorphous carbon, silicon carbide, and hydrocar- bons. Multiple dust grain types are sometimes produced in the same system. CO formation in novae may not reach saturation, thus in- validating the usual paradigm in which the C:O ratio determines the dust species. A few novae, such as V705 Cas and DZ Cru, have ex- hibited emission features near 6, 8, and 11 µm that are similar to \"Unidentified Infrared\" (UIR) features, but with significant differences in position and band structure. Here, we present Spitzer IRS spectra of two recent dusty novae, V2361 Cyg and V2362 Cyg, that harbor similar peculiar emission structures superimposed on features arising from carbonaceous grains. In other astronomical objects, such as star forming regions and young stellar objects, emission peaks at 6.2, 7.7, and 11.3 µm have been associated with polycyclic aromatic hydro- carbon (PAH) complexes. We suggest that hydrogenated amorphous carbon (HAC) may be the source of these features in novae based upon the spectral behavior of the emission features and the conditions under which the dust formed.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128600299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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