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Isoviolanthrene (C34H18), a polycyclic aromatic hydrocarbon (PAH) molecule, was studied via matrix isolation in argon and water at 20 K. Infrared spectroscopy was performed in situ where samples were irradiated using ultraviolet light. Experimental spectra were compared to theoretical spectra for vibrational band assignment, determination of the corresponding A-values, and photoproduct identification. Isoviolanthrene was also deposited as a thin film and irradiated with different energy sources: ultraviolet photons (10.2 eV), soft electrons (1.5 keV), protons (1.5 MeV), and He+ particles (1.5 MeV), to understand the effects of different energy sources on a PAH. Anions and cations of isoviolanthrene were produced as a result of UV photolysis in an argon matrix. Hydrogen- and oxygen-rich aromatic photoproducts were produced by ultraviolet photons when isoviolanthrene was isolated in a water matrix. The irradiated PAH thin films results were dependent on the energy source. Irradiation with ultraviolet photons yielded a broad underlying feature centered at 9.6 μm, while bombardment with soft electrons gave a broad feature centered at 7.7 μm. In the case of proton bombardment, no broad feature was detected, in contrast with He+ bombardment that destroyed most of the isoviolanthrene and produced broad features in the C-Hoop and C–H stretching regions. A comparison of astronomical IR emission observations with our experimental results in the mid-infrared range has revealed a similarity between the observed plateaus and the broad features produced by our experiments. [ABSTRACT FROM AUTHOR]

Sonoluminescence is the phenomenon in which acoustic energy is (partially) transformed into light as a bubble of gas collapses inside a liquid medium. One particular model used to explain the motion of the bubble’s wall forced by acoustic pressure is expressed by the Rayleigh–Plesset equation, which can be obtained from the Navier–Stokes equation. In this article, we describe an alternative approach to derive the Rayleigh–Plesset equation based on Lagrangian mechanics. This work is addressed mainly to undergraduate students and teachers. It requires knowledge of calculus and of many concepts from various fields of physics at the intermediate level. [ABSTRACT FROM AUTHOR]

This work presents the photochemistry of ultraviolet (UV) irradiated coronene in water ices at 15 K studied using mid-infrared Fourier transform (FTIR) spectroscopy for C24H12:H2O at concentrations of (1:50), (1:150), (1:200), (1:300), and (1:400). Previous UV irradiation studies of anthracene:H2O, pyrene:H2O, and benzo[ghi]perylene:H2O ices at 15 K have shown that aromatic alcohols and ketones, as well as CO2 and H2CO, are formed at very low temperatures. Likewise, here, in addition to the coronene cation, hydroxy-, keto-, and protonated coronene (coronene H+) are formed. The rate constants for the decay of neutral coronene and for the formation of photoproducts have been derived. It is shown that Polycyclic Aromatic Hydrocarbons (PAHs) and their UV induced PAH:H2O photoproducts have mid-infrared spectroscopic signatures in the 5–8 μm region that can contribute to the interstellar ice components described by Boogert et al. as C1–C5. Our results suggest that oxygenated and hydrogenated PAHs could be in UV-irradiated regions of the interstellar medium where water-rich ices are important. [ABSTRACT FROM AUTHOR]

Solid water has been observed on the surface of many different astronomical objects and is the dominant ice present in the universe, from the solar system (detected on the surface of some asteroids, planets and their satellites, trans-Neptunian objects [TNOs], comets, etc.) to dense cold interstellar clouds (where interstellar dust grains are covered with water-rich ices). Ethane has been detected across the solar system, from the atmosphere of the giant planets and the surface of Saturn’s satellite Titan to various comets and TNOs. To date, there were no experiments focused on icy mixtures of C2H6 and H2O exposed to ion irradiation simulating cosmic rays, a case study for many astronomical environments in which C2H6 has been detected. In this work, the radiolysis of a C2H6:H2O (2:3) ice mixture bombarded by a 40 MeV58Ni11+ ion beam is studied. The chemical evolution of the molecular species existing in the sample is monitored by a Fourier transform infrared spectrometer. The analysis of ethane, water, and molecular products in solid phase was performed. Induced chemical reactions in C2H6:H2O ice produce 13 daughter molecular species. Their formation and dissociation cross sections are determined. Furthermore, atomic carbon, oxygen, and hydrogen budgets are determined and used to verify the stoichiometry of the most abundantly formed molecular species. The results are discussed in the view of solar system and interstellar medium chemistry. The study presented here should be regarded as a first step in laboratory works dedicated to simulate the effect of cosmic radiation on multicomponent mixtures involving C2H6 and H2O. [ABSTRACT FROM AUTHOR]

The participation of condensed nitrogen in the surface chemistry of some objects in the outer solar system, such as Pluto and Triton, is very important. The remote observation of this species using absorption spectroscopy is a difficult task because N2 is not IR active in the gas phase. Water is also among the most abundant molecules in the surface of these objects; chemical reactions between N2 and H2O induced by cosmic rays are therefore expected. Although pure N2 ice is hardly identified by IR spectroscopy, the species produced through the processing of the surface ice by cosmic rays may give relevant clues indicating how abundant the N2 is in the outside layers of the surface of trans-Neptunian objects (TNOs). The objective of this work is to investigate the formation of nitrogenated species induced by cosmic-ray analogs in an ice mixture containing nitrogen and water. Experiments were performed in the GANIL Laboratory by bombarding N2:H2O (10:1) ice at 15 K with 40 MeV 58Ni11+ ions. Evolution of precursor and daughter species was monitored by Fourier transform infrared spectrometry. The main produced species are the nitrogen oxides NOk (k = 1–3), N2Oj (j = 1–5), N3, and O3. Among them, the N2O and N3 are the most abundant, representing ∼61% of the total column density of the daughter molecules at 1013 ions cm−2 fluence; the current results indicate that the yield of daughter species from this mixture is low, and this may be one of the reasons why NiOj molecules are not usually observed in TNOs. [ABSTRACT FROM AUTHOR]