Article
Astronomy & Astrophysics
Jen-Iu Lo, Hsiao-Chi Lu, Wei-Hsiu Hung, J. F. Ogilvie, Bing-Ming Cheng
Summary: We report the spectra of molecular oxygen in the visible, near-infrared, and mid-infrared wavelength ranges at different temperatures. Different features, such as sharp lines and triplets, were observed depending on the temperature. The transmission of solid oxygen also showed temperature-dependent behavior, with a significant absorption observed in the mid-infrared range.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Jen-Iu Lo, Hsiao-Chi Lu, Wei-Hsiu Hung, J. F. Ogilvie, Bing-Ming Cheng
Summary: The spectroscopy of solids alpha- and beta-oxygen has been established through thermal ramping spectra measurements of solid O2. The study focused on the visible, near-infrared, and mid-infrared wavelength regions. The presence of imperfect crystallinity in solid O2 ice was also observed. The spectra of the solids alpha- and beta-oxygen showed similarities in the visible region but differed significantly from that of the imperfect structure-contaminated solid O2.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Venkata Lakshmi Karri, Sumalya Kaluva, Ajay Chaudhari, Takashi Onaka, Mahadevappa Naganathappa
Summary: This paper discusses the infrared features of C-24 based on density functional theory calculation and suggests that some features observed in celestial objects may be attributed to C-24. The electronic absorption spectra of C-24 isomers are calculated and compared with the bump feature at 217 nm in the interstellar extinction curve. Four groups of C-24 isomers, namely cage, planar, bowl, and ring forms, are considered in neutral and charged states. The study reveals significant changes in infrared and electronic absorption spectra, as well as structural parameters, upon ionization.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Spectroscopy
P. A. S. Randi, D. F. Pastega, M. H. F. Bettega, N. C. Jones, S. V. Hoffmann, S. Eden, A. Souza Barbosa, P. Limao-Vieira
Summary: Absolute cross-section values of gas-phase formic acid in the VUV range have been measured and analyzed, revealing previously unreported vibronic features and active vibrational modes. The photoabsorption measurements also provide information on the photolysis lifetime of formic acid at different altitudes. The combination of experimental and theoretical methods allows for a comprehensive understanding of the electronic transitions and potential energy curves.
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
(2023)
Article
Astronomy & Astrophysics
Ugo Jacovella, Christopher S. Hansen, Alexandre Giuliani, Adam J. Trevitt, Laurent Nahon
Summary: This paper investigates the photostability of protonated N-hetero(poly)acenes and their ability to retain N atoms. The results suggest that these protonated compounds are unlikely precursors for larger nitrogen-containing species in interstellar space, but may serve as possible substrates for prebiotic chemistry in planetary atmospheres.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
F. D. Priestley, A. P. Whitworth
Summary: Research suggests that collisions between interstellar gas clouds can rapidly generate large masses of dense gas, triggering star formation. By analyzing molecular line observations and conducting simulations, it is possible to distinguish genuinely colliding clouds from chance superpositions, and confirm observational evidence of cloud collisions.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
F. D. Priestley, D. Arzoumanian, A. P. Whitworth
Summary: Filamentary structures in molecular clouds, which are important for star formation, are expected to form where the supersonic turbulent velocity field converges. While the existing model reproduces some properties of these structures, it is unclear whether it can reproduce their kinematic features. In this study, we use modeling to predict the emission properties of dynamically forming filaments, and the results are largely consistent with observations, suggesting that equilibrium analysis and simulations assuming the existence of filaments may be unrealistic.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Susana Iglesias-Groth
Summary: We used Spitzer Space Telescope spectra to search for the aromatic amino acid tryptophan in the interstellar gas of the young star cluster IC 348. We found emission lines in the observed spectrum that are consistent with the laboratory measurements of tryptophan. The presence of these lines in multiple interstellar locations suggests that the molecule causing the emission is widespread in interstellar space.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
A. Maragkoudakis, E. Peeters, A. Ricca, C. Boersma
Summary: This study examines the dependence of polycyclic aromatic hydrocarbon (PAH) band intensity ratios on the average number of carbon atoms and assesses their effectiveness as tracers for PAH size using the NASA Ames PAH Infrared Spectroscopic Database. The research finds that band ratios including the 3.3 μm PAH band provide the best PAH size tracers for small-to-intermediate sized PAHs. Additionally, band ratios including the sum of the 15-20 μm PAH features and the 6.2 or 7.7 μm bands also serve as good tracers for PAH size in this range.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Ugo Jacovella, Jennifer A. Noble, Alexandre Guliani, Christopher S. Hansen, Adam J. Trevitt, Julie Mouzay, Isabelle Couturier-Tamburelli, Nathalie Pietri, Laurent Nahon
Summary: The photodestruction of protonated benzonitrile under UV and VUV radiation leads to the formation of a highly reactive cationic species, C6H5+, which is predicted to be an important precursor of larger aromatic molecules in space.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Ameek Sidhu, Josh Bazely, Els Peeters, Jan Cami
Summary: PCA analysis was conducted on the fluxes of five PAH bands in the reflection nebula NGC 7023. The results showed that two principal components explained most of the observed variance in PAH fluxes. The first component represented total PAH emission while the second component was related to the ionization state of the PAHs. The analysis also revealed the presence of two subsets of ionized bands in the PDR but not in the cavity.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
A. Maragkoudakis, E. Peeters, A. Ricca
Summary: This study examines the variations in spectral characteristics and intensities of polycyclic aromatic hydrocarbons (PAHs) in two different scenarios of PAH processing: destruction of small PAHs or formation of large PAHs, and vice versa. PAH emission was measured with and without plateau components. The results show that smaller PAHs have a larger impact on the PAH band strengths, and smaller PAHs primarily contribute to plateau emission. The 7.7/(11.0 + 11.2) μm PAH band ratio is the best choice for tracing PAH charge, and the 3.3/(11.2 + 11.0) μm PAH band ratio is efficient for both tracing PAH size and characterizing the dominant processing or formation scenario.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
B. Kerkeni, I Garcia-Bernete, D. Rigopoulou, D. P. Tew, P. F. Roche, D. C. Clary
Summary: In this study, we extend the prediction of vibrational spectra to large-sized polycyclic aromatic hydrocarbon (PAH) molecules using various computational chemistry methodologies. The impact of PAH size on vibrational band positions is investigated through global optimizations and frequency calculations. A general Frequency Scaling Function (FSF) is developed to shift the bands and provide a systematic comparison. The emergence of new features in large PAHs and changes in the intensity of certain features are observed. Trends in the PAH band ratio as a function of radiation intensity are also explored.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Xiaoyi Hu, Deping Zhang, Congcong Zhang, Yuanyuan Yang, Yang Chen, Junfeng Zhen, Liping Qin
Summary: This study focuses on the growth process of fullerene/9-aminoanthracene clusters, investigating the competition between the van der Waals bonding growth, covalent bonding growth model, and charge transfer model in the formation of large clusters. Experimental results show efficient formation of cluster cations under specific conditions, with nitrogen playing a crucial role in cluster formation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Luis Alvarez-Thon, Timothy J. Lee, Ryan C. Fortenberry, Natalia Inostroza-Pino
Summary: This study calculates the aromaticity of cyclic hydrocarbon molecules using the ring current strength (RCS) value, aiming to predict their detectability in astrophysical media. Known interstellar molecules exhibit high RCS values, while those with low or negative values have not yet been observed, indicating the significance of this metric in astrophysical studies.
ASTRONOMY & ASTROPHYSICS
(2022)
