Infrared spectra and optical constants of astronomical ices: I. Amorphous and crystalline acetylene

Hudson, R. L.; Ferrante, R. F.; Moore, M. H.

doi:10.1016/j.icarus.2013.08.029

Cited by 85 publications

(80 citation statements)

References 45 publications

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“…To determine pure C 2 H x ice thicknesses with IR spectroscopy, we used post-deposition IR spectra and hydrocarbon band strengths. Band strengths relevant for the C 2 H x hydrocarbons in our set are reported in Hudson et al (2014a), Hudson et al (2014b), and Gerakines et al (1995) (Fig. 1, left panel).…”

Section: Ice Thicknessessupporting

confidence: 65%

Desorption Kinetics and Binding Energies of Small Hydrocarbons

Behmard

Fayolle

Graninger

et al. 2019

ApJ

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Small hydrocarbons are an important organic reservoir in protostellar and protoplanetary environments. Constraints on desorption temperatures and binding energies of such hydrocarbons are needed for accurate predictions of where these molecules exist in the ice vs. gas-phase during the different stages of star and planet formation. Through a series of temperature programmed desorption (TPD) experiments, we constrain the binding energies of 2 and 3-carbon hydrocarbons (C 2 H 2 -acetylene, C 2 H 4 -ethylene, C 2 H 6 -ethane, C 3 H 4 -propyne, C 3 H 6 -propene, and C 3 H 8 -propane) to 2200-4200 K in the case of pure amorphous ices, to 2400-4400 K on compact amorphous H 2 O, and to 2800-4700 K on porous amorphous H 2 O. The 3-carbon hydrocarbon binding energies are always larger than the 2-carbon hydrocarbon binding energies. Within the 2and 3-carbon hydrocarbon families, the alkynes (i.e., least-saturated) hydrocarbons exhibit the largest binding energies, while the alkane and alkene binding energies are comparable. Binding energies are ∼5-20% higher on water ice substrates compared to pure ices, which is a small increase compared to what has been measured for other volatile molecules such as CO and N 2 . Thus in the case of hydrocarbons, H 2 O has a less pronounced effect on sublimation front locations (i.e., snowlines) in protoplanetary disks.

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Section: Ice Thicknessessupporting

confidence: 65%

Desorption Kinetics and Binding Energies of Small Hydrocarbons

Behmard

Fayolle

Graninger

et al. 2019

ApJ

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“…We used a number density of 1.76×10 22 molecules·cm -3 derived from the mass density, assuming a value of 0.76 g·cm -3 (Hudson et al, 2014;McMullan et al, 1992), Avogadro's number and the molar mass of acetylene (26.04 g·mol -1 ). We calculated an average thickness of the acetylene ice film to be between 15 nm and 20 nm, based on minor variations in the deposition conditions that reflect in acetylene absorbance at 3225 cm -1 .…”

Section: Quantification Of C2h2 Ice Desorptionmentioning

confidence: 99%

“…We have chosen to first focus on T 1tholin, which has higher nitrogen incorporation than the T 5 -tholin. The evolution of the acetylene amount on the sample was monitored using its infrared band at 3225 cm -1 , attributed to the υ 3 vibrational stretching mode of the C-H bond (Hudson et al, 2014). Figure 4 presents the evolution of the differential absorbance after each irradiation for pure C 2 H 2 in the left panel and for C 2 H 2 deposited on a T 1 -tholin sample in the right panel.…”

Section: Pure C2h2-ice and C2h2 On T1-tholinmentioning

confidence: 99%

“…A is the band-strength (cm·molecule -1 ). For our calculation, we used a band strength value of 3.58×10 -17 cm.molecule -1 for the 3225 cm -1 band calculated by Hudson et al (2014) for the crystalline acetylene at 70 K. In our experiments, the N 0 values are found to be 2.89×10 16 molecules·cm -2 . We obtained on an average a desorption rate of (2.1 ± 0.2) ×10 -6 molecules·photon -1 averaged on the total irradiation time at 355 nm.…”

Section: Photodesorption Rates and Implications For Titanmentioning

confidence: 99%

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Photoreactivity of condensed acetylene on Titan aerosols analogues

Fleury

Gudipati

Couturier-Tamburelli

et al. 2019

Icarus

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Volatile organic molecules formed by photochemistry in the upper atmosphere of Titan can undergo condensation as pure ices in the stratosphere and the troposphere as well as condense as ice layers onto the organic aerosols that are visible as the haze layers of Titan. As solar photons penetrate through Titan's atmosphere, shorter-wavelength photons are attenuated and longerwavelength photons make it into the lower altitudes, where aerosols become abundant. We conducted an experimental study to evaluate the long wavelength (λ > 300 nm) photo-reactivity of these ices accreted on the Titan aerosol-analogs (also known as tholins) made in the laboratory. We have focused on acetylene, the third most abundant hydrocarbon in Titan's atmosphere (after CH 4 and C 2 H 6 ). Further, acetylene is the most abundant unsaturated hydrocarbon in Titan's atmosphere. Our results indicate that the aerosols can act as activation centers to drive the photoreactivity of acetylene with the aerosols at the accretion interface at wavelengths where acetylene-ice alone does not show photoreactivity. We found that along with photochemistry, photodesorption plays an important role. We observed that about 15% of the initial acetylene is photodesorbed, with a photodesorption rate of (2.1 ± 0.2) × 10 -6 molecules·photon -1 at 355 nm. This photodesorption is wavelength-dependent, confirming that it is mediated by the UV absorption of the aerosol analogues, similar to photochemistry. We conclude that the UV-Vis properties of aerosols would determine how they evolve further in Titan's atmosphere and on the surface through photochemical alterations involving longerwavelength photons. Stronger extinction coefficients in the longer wavelength UV-Vis regions (>300 nm) of the aerosol give higher efficiencies of photodesorption of accreted volatiles as well as photochemical incorporation of unsaturated condensates (such as acetylene) into the aerosols.

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“…−17 cm/molecule (mean from Hudson et al 2014;Knez et al 2012;Khanna et al 1988;Boudin et al 1998). A √ 2 correction factor has been applied to obtain normal column densities, taking into account that the IR measurements were performed under 45…”

Section: Infrared Measurementsmentioning

confidence: 99%

Swift heavy ion irradiation of interstellar dust analogues

Dartois

Chabot

Pino

et al. 2017

A&A

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Context. Interstellar dust grain particles are immersed in vacuum ultraviolet (VUV) and cosmic ray radiation environments influencing their physicochemical composition. Owing to the energetic ionizing interactions, carbonaceous dust particles release fragments that have direct impact on the gas phase chemistry. Aims. The exposure of carbonaceous dust analogues to cosmic rays is simulated in the laboratory by irradiating films of hydrogenated amorphous carbon interstellar analogues with energetic ions. New species formed and released into the gas phase are explored. Methods. Thin carbonaceous interstellar dust analogues were irradiated with gold (950 MeV), xenon (630 MeV), and carbon (43 MeV) ions at the GSI UNILAC accelerator. The evolution of the dust analogues is monitored in situ as a function of fluence at 40, 100, and 300 K. Effects on the solid phase are studied by means of infrared spectroscopy complemented by simultaneously recording mass spectrometry of species released into the gas phase. Results. Specific species produced and released under the ion beam are analyzed. Cross sections derived from ion-solid interaction processes are implemented in an astrophysical context.

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Infrared spectra and optical constants of astronomical ices: I. Amorphous and crystalline acetylene

Cited by 85 publications

References 45 publications

Desorption Kinetics and Binding Energies of Small Hydrocarbons

Desorption Kinetics and Binding Energies of Small Hydrocarbons

Photoreactivity of condensed acetylene on Titan aerosols analogues

Swift heavy ion irradiation of interstellar dust analogues

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