Article
Astronomy & Astrophysics
Haoyu Fan, Madison Schwartz, Amin Farhang, Nick L. J. Cox, Pascale Ehrenfreund, Ana Monreal-Ibero, Bernard H. Foing, Farid Salama, Klay Kulik, Heather MacIsaac, Jacco Th van Loon, Jan Cami
Summary: More than 500 diffuse interstellar bands (DIBs) have been observed and studied to reveal the nature of their carriers. Researchers have found anticorrelated DIB pairs and redefined DIB families using clustering algorithms. They also discovered a continuous sequence of DIBs and identified at least two factors influencing the dissimilarities between them.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
J. N. Frereux, M. Godard, E. Dartois, T. Pino
Summary: Based on the UV spectra of various carbonaceous molecules, this study suggests that naphthalene and its derivatives with specific mass progression and characteristic electronic absorption band profile may be good candidates as carriers of the interstellar bump feature.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Victoria H. J. Clark, David M. Benoit
Summary: The hybrid CCSD(T) + PBE-D3 approach is proposed for calculating the vibrational signatures of gas-phase benzene and benzene adsorbed on a water ice surface, demonstrating the importance of including a surface in spectroscopic calculations. Results show that the hybrid approach outperforms the PBE-D3-only methods in capturing the vibrational modes and frequencies in both gaseous and adsorbed benzene systems.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
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
Astronomy & Astrophysics
Cristopher Heyser Valencia, Natalia Inostroza-Pino
Summary: This study investigates the formation pathways to complex organic molecules when a OH+ projectile hits an interstellar dust grain covered only by methanol molecules using ab initio molecular dynamics simulations. The results show that methanediol and hydroxymethyl play a key role in the formation of stable complex organic molecules.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
H. R. Hrodmarsson, E. F. van Dishoeck
Summary: In order to accurately characterize and constrain the photodissociation and photoionization rates in different radiation fields, it is necessary to measure the cross sections of individual atoms and molecules. This study updates the Leiden VUV photodissocation and photoionization cross section database by including new cross sections for radicals and expanding it with several astronomically relevant species.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Jonathan M. C. Rawlings, D. A. Williams
Summary: The deposition of water ice onto grains in interstellar clouds is found to have a correlation with visual extinction above a certain threshold, potentially influenced by the balance of oxygen atom freeze-out and H2O molecule photodesorption. The phenomenon suggests a common cause across different regions with similar chemical and dynamical evolution, while the variability in A(th) values may be attributed to differences in local radiation field strength.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Marco Monaci, Loris Magnani, Steven N. N. Shore
Summary: This study aims to investigate the mixing of dust and gas in the interstellar medium using two independent strategies to calculate the column densities of molecular and atomic gases, and to determine the dust-to-gas mixing ratio.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Jonathan M. C. Rawlings
Summary: The standard model of cosmic ray heating-induced desorption of interstellar ices has been re-evaluated and developed, finding that the desorption rates are significantly larger than previously determined. The dominant contribution to desorption comes from the smallest grains in typical interstellar grain size distributions. The model suggests that if the interval between cosmic ray impacts is shorter than the freeze-out time-scale, the continuous representation is inapplicable.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Qi Lin, X. J. Yang, Aigen Li
Summary: The exact nature of the 2175 angstrom extinction bump has remained unknown since its discovery in 1965. Popular candidates for the carrier of the extinction bump include nano-sized graphitic grains and polycyclic aromatic hydrocarbon (PAH) molecules. This study uses quantum chemical computations to evaluate PAHs as a possible carrier and finds that a mixture of PAHs can reproduce the features of the 2175 angstrom bump.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Zainab Awad, Serena Viti
Summary: Observations of diffuse clouds have found high abundances of simple hydrocarbons, challenging conventional gas-phase chemical models. Recent experimental results suggest that photodecomposition of hydrogenated amorphous carbon (HAC) and solid hexane can release a range of hydrocarbons into the gas phase. This study explores the feasibility of a 'top-down' or degradation mechanism for the formation of simple hydrocarbons in diffuse clouds.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
T. P. Nie, F. Y. Xiang, Aigen Li
Summary: Since their first detection over 100 years ago, the diffuse interstellar bands (DIBs) have remained largely unidentified. Recent research suggests that gas-phase buckminsterfullerene ions (C-60(+)) may be a promising carrier for these DIBs. This study analyzes astronomical data and identifies four DIBs, supporting the hypothesis that C-60(+) is the carrier for two of these DIBs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Qian Wang, X. J. Yang, Aigen Li
Summary: The central wavelength of the mysterious 2175 angstrom extinction bump remains constant, but the bandwidth varies. Recent studies show that the extinction bump exhibits shifts from the canonical wavelength. By taking a physical approach, the derived UV extinction curve for each line of sight is found to have a wavelength around 2200 angstrom, with smaller scatters than previous studies but still larger than the nominal bump position of 2175 angstrom.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Chamani M. Gunasekera, Xihan Ji, Marios Chatzikos, Renbin Yan, Gary Ferland
Summary: This study investigates the impact of dust depletion on the spectral-line ratio predictions and structure of the H ii region in the Orion Nebula. The results show that the intensity of line ratios is affected by depletions onto dust grains, and adjusting dust abundances along with depletion affects the structure and overall temperature of the H+ layer.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Hiroyuki Hirashita, Vladimir B. Il'in, Laurent Pagani, Charlene Lefevre
Summary: The properties of interstellar grains, such as size distribution and porosity, are influenced by interactions such as coagulation and shattering in the interstellar medium. The balance between shattering and coagulation determines the porosity of grains, impacting extinction and creation of porous grains. The interplay between these processes is crucial for understanding grain evolution in the interstellar medium.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
G. Molpeceres, I. Jimenez-Serra, Y. Oba, T. Nguyen, N. Watanabe, J. Garcia de la Concepcion, B. Mate, R. Oliveira, J. Kaestner
Summary: This article discusses the isomerism of organic molecules in the interstellar medium and the mechanisms behind it. By conducting experiments and calculations, the study explores the isomerization processes of formic and thioformic acid, as well as the feasibility of their deuterated counterparts. The results reveal that the trans isomer is more stable on interstellar dust grains, and both isomers of thioformic acid exhibit higher reactivity. The study also highlights the impact of reaction orientations on the isomerization rate.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Satoshi Ohashi, Claudio Codella, Nami Sakai, Claire J. Chandler, Cecilia Ceccarelli, Felipe Alves, Davide Fedele, Tomoyuki Hanawa, Aurora Duran, Cecile Favre, Ana Lopez-Sepulcre, Laurent Loinard, Seyma Mercimek, Nadia M. Murillo, Linda Podio, Yichen Zhang, Yuri Aikawa, Nadia Balucani, Eleonora Bianchi, Mathilde Bouvier, Gemma Busquet, Paola Caselli, Emmanuel Caux, Steven Charnley, Spandan Choudhury, Nicolas Cuello, Marta De Simone, Francois Dulieu, Lucy Evans, Siyi Feng, Francesco Fontani, Logan Francis, Tetsuya Hama, Eric Herbst, Shingo Hirano, Tomoya Hirota, Muneaki Imai, Andrea Isella, Izaskun Jimenez-Serra, Doug Johnstone, Claudine Kahane, Romane Le Gal, Bertrand Lefloch, Luke T. Maud, Maria Jose Maureira, Francois Menard, Anna Miotello, George Moellenbrock, Shoji Mori, Riouhei Nakatani, Hideko Nomura, Yasuhiro Oba, Ross O'Donoghue, Yuki Okoda, Juan Ospina-Zamudio, Yoko Oya, Jaime Pineda, Albert Rimola, Takeshi Sakai, Dominique Segura-Cox, Yancy Shirley, Brian Svoboda, Vianney Taquet, Leonardo Testi, Charlotte Vastel, Serena Viti, Naoki Watanabe, Yoshimasa Watanabe, Arezu Witzel, Ci Xue, Bo Zhao, Satoshi Yamamoto
Summary: This study investigates the low-mass Class 0 multiple system VLA 1623AB in the Ophiuchus star-forming region, focusing on its velocity fields and rotation motion. The analysis reveals the rotation motion in the envelope and the velocity gradients in the outflows. The study also examines the alignment of the circumbinary disks and their relation to the large-scale outflow and magnetic field. Additionally, a velocity gradient associated with rotation is detected towards the VLA 16293B disk, opposite to the gradient observed in the larger-scale envelope, outflow, and circumbinary disk.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Kenji Furuya, Tetsuya Hama, Yasuhiro Oba, Akira Kouchi, Naoki Watanabe, Yuri Aikawa
Summary: The activation energies for desorption and surface diffusion of adsorbed molecules on dust grains are important parameters in interstellar chemistry. While the desorption activation energy can be measured in the laboratory, the data for the surface diffusion activation energy is limited. In this study, the researchers experimentally measured the surface diffusion activation energy for several adsorbed species on water-ice surfaces and found that the scaling factor ranges from 0.2 to 0.7 depending on the species. They also conducted multiple simulations to address the uncertainties and identified key species for further investigation.
ASTROPHYSICAL JOURNAL LETTERS
(2022)
Review
Biochemistry & Molecular Biology
Tolga N. Karsili, Barbara Marchetti, Marsha Lester, Michael N. R. Ashfold
Summary: This article reviews the current knowledge about the electronic spectroscopy of Criegee intermediates (CIs), with a focus on atmospherically relevant CIs and conjugated carbene-derived CIs of interest in synthetic chemistry. The article also summarizes the photochemical data reported to date, including studies on photo-induced fission of the terminal O-O bond and speculations about possible alternate decay processes for CIs following non-adiabatic coupling and dissociation.
PHOTOCHEMISTRY AND PHOTOBIOLOGY
(2023)
Article
Chemistry, Physical
Naoki Numadate, Shota Saito, Yuki Nojima, Taka-aki Ishibashi, Shinichi Enami, Tetsuya Hama
Summary: Ultraviolet photolysis of fatty acid surfactants can generate hydroxyl radicals, but the dimerization structure of nonanoic acid's surface inhibits its photochemical reactivity.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Chemistry, Applied
Makoto Uyama, Shinya Okabe, Takumi Kurashima, Rie Kurinobu, Miwa Takechi, Ryo Yoshiba, Rina Miyoshi, Seigi Noda, Mio Kaneko, Yuka Ikemoto, Atsushi Takahara, Yuji Higaki, Tetsuya Hama
Summary: The combined use of GA and GCA enhances the hair straightening effect of GA and increases the penetration amount of GA into human hair. GA primarily accumulates in the innermost region of the hair, the medulla, and disappears after a hair straightener treatment at 180 degrees C due to a chemical reaction. Therefore, developing a GA penetration-enhancing agent to reduce the GA concentration in products is crucial.
INTERNATIONAL JOURNAL OF COSMETIC SCIENCE
(2023)
Article
Astronomy & Astrophysics
Thanh Nguyen, Yasuhiro Oba, W. M. C. Sameera, Kenji Furuya, Akira Kouchi, Naoki Watanabe
Summary: This study examined the surface reactions of CH3SH with H atoms on solid water and found that CH4 is the main product, while minor products include CH2SH and CH3S radicals.
ASTROPHYSICAL JOURNAL
(2023)
Review
Multidisciplinary Sciences
Masashi Tsuge, Naoki Watanabe
Summary: Molecular clouds in space are where various molecular species are born, and chemical reactions on icy dust grain surfaces play a crucial role in their formation. Laboratory experiments conducted under low-temperature, high-vacuum conditions have revealed the importance of radical reactions on icy dust grain surfaces and the formation of abundant molecules such as H2, H2O, H2CO, CH3OH, and deuterium fractionation processes. The development of sensitive, non-destructive methods for detecting adsorbates and clarifying the behavior of free radicals on ice, which contribute to the formation of complex organic molecules, is also discussed.
PROCEEDINGS OF THE JAPAN ACADEMY SERIES B-PHYSICAL AND BIOLOGICAL SCIENCES
(2023)
Article
Astronomy & Astrophysics
Y. Nakai, W. M. C. Sameera, K. Furuya, H. Hidaka, A. Ishibashi, N. Watanabe
Summary: We conducted experimental investigations on the formation of methanol through the reactions of low-energy CH3 (+) ions with an amorphous solid water (ASW) surface at temperatures around 10 K. The results showed that methanol molecules were produced by the ion irradiation and that the hydroxy groups in methanol originated from water molecules in the ASW. Molecular dynamics simulations confirmed the spontaneous production of methanol and H3O+ ions regardless of the contact point of CH3 (+) on the ASW surface. Furthermore, astrochemical modelling demonstrated the limited impact of this reaction on the abundance of methanol in molecular clouds.
ASTROPHYSICAL JOURNAL
(2023)
Article
Chemistry, Physical
Akira Kouchi, Tomoya Yamazaki, Hiroyasu Katsuno, Hiroki Nada, Tetsuya Hama, Yuki Kimura
Summary: By using cryogenic transmission electron microscopy, the annealing process of -50-nm sized ice Ic islands on an amorphous SiN substrate at 100-130 K was observed. It was found that water molecules diffused freely on the surface of ice Ic and amorphous SiN, leading to the coarsening of islands. Additionally, it was observed that hydrogen-ordered cubic ices grew on the surface of ice Ic islands during coarsening. Hydrogen-ordered cubic ices may exist on various objects in space.
Article
Chemistry, Physical
Reo Sato, So Taniguchi, Naoki Numadate, Tetsuya Hama
Summary: Ice I has three forms: hexagonal ice I-h, cubic ice I-c, and stacking disordered ice I-sd. The formation of ice I is inhibited at temperatures below 60K, and amorphous water becomes metastable. The newly developed RHEED technique reveals that ice I-c can form through Ne sublimation at 13K. The extent of stacking disorder in Ne matrix sublimation ice is smaller than vapor-deposited ice I-sd prepared at 143K and below the limit of detection of low-temperature RHEED.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Multidisciplinary Sciences
Hiromasa Niinomi, Tomoya Yamazaki, Hiroki Nada, Tetsuya Hama, Akira Kouchi, Tomoya Oshikiri, Masaru Nakagawa, Yuki Kimura
Summary: Experimental evidence has been provided for the existence of an unknown water at the ice V-water interface, which is immiscible with the surrounding water. The dewetting dynamics of this unknown water resembles spinodal-like behavior, with a characteristic velocity of approximately 90 m/s. The time evolution of the characteristic length of the spinodal-like undulation suggests that the dynamics can be described using a common model for spinodal decomposition of an immiscible liquid mixture, and the unknown water transiently exhibits anisotropy, indicating liquid crystal properties.
SCIENTIFIC REPORTS
(2023)
Article
Multidisciplinary Sciences
Shota Saito, Naoki Numadate, Hidemasa Teraoka, Shinichi Enami, Hirokazu Kobayashi, Tetsuya Hama
Summary: Saturated fatty acids in oceans can undergo photochemical reactions induced by solar radiation to produce volatile organic compounds, which are precursors of secondary organic aerosols. However, the absorption of longer wavelengths by liquid saturated fatty acids is still not fully understood.
Article
Chemistry, Physical
Stuart W. Crane, Jason W. L. Lee, Michael N. R. Ashfold, Daniel Rolles
Summary: Coulomb explosion imaging (CEI) methods are increasingly used to explore and distinguish the static stereo-configurations of small quantum systems. By using ultrafast laser pulses, CEI experiments can track the time-evolution of molecular structures and advance understanding of molecular fragmentation processes. This Perspective highlights two emerging families of dynamical studies: 'one-colour' studies and 'two-colour' studies, which provide new insights into molecular fragmentation processes and charge transfer processes with better stereochemical control.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
W. M. C. Sameera, Avon P. Jayaweera, Atsuki Ishibashi, Hiroshi Hidaka, Yasuhiro Oba, Naoki Watanabe
Summary: A systematic mechanistic survey was conducted for the CH3OH + OH reaction on ice. The study found a range of binding energies for CH2OH radical and CH3OH molecule on hexagonal water ice and amorphous solid water. The multi-component artificial force-induced reaction method determined the reaction mechanisms and confirmed the formation of CH2OH and CH3O radicals. The results highlight the significance of the binding site or reaction site in determining the computed binding energies and reaction barriers.
FARADAY DISCUSSIONS
(2023)
