Variations in the strength of the infrared forbidden 2328.2 cm-1 fundamental of solid N2 in binary mixtures

Radiolysis of N2-rich astrophysical ice by swift oxygen ions: implication for space weathering of outer solar system bodies

In order to investigate the role of medium mass cosmic rays and energetic solar particles in the processing of N₂-rich ice on frozen moons and cold objects in the outer solar system, the bombardment of an N₂ : H₂O : NH₃ : CO₂ (98.2 : 1.5 : 0.2 : 0.1) ice mixture at 16 K employing 15.7 MeV ¹⁶O⁵⁺ was performed. The changes in the ice chemistry were monitored and quantified by Fourier transformed infrared spectroscopy (FTIR). The results indicate the formation of azide radicals (N₃), and nitrogen oxides, such as NO, NO₂, and N₂O, as well as the production of CO, HNCO, and OCN^-. The effective formation and destruction cross-sections are roughly on the order of 10^-12 cm² and 10^-13 cm², respectively. From laboratory molecular analyses, we estimated the destruction yields for the parent species and the formation yields for the daughter species. For N₂, this value was 9.8 × 10⁵ molecules per impact of ions, and for the most abundant new species (N₃), it was 1.1 × 10⁵ molecules per impact of ions. From these yields, an estimation of how many species are destroyed or formed in a given timescale (10⁸ years) in icy bodies in the outer solar system was calculated. This work reinforces the idea that such physicochemical processes triggered by cosmic rays, solar wind, and magnetospheric particles (medium-mass ions) in nitrogen-rich ices may play an important role in the formation of molecules (including pre-biotic species precursors such as amino acids and other "CHON" molecules) in very cold astrophysical environments, such as those in the outer region of the solar system (e.g. Titan, Triton, Pluto, and other KBOs).

Activation of weak IR fundamentals of two species of astrochemical interest in the Td point group – the importance of amorphous ices

Infrared spectra are reported showing the nominally-forbidden ν₁ and ν₂ fundamentals of amorphous CH₄, a solid of considerable astrochemical interest.

Novel measurements of refractive index, density and mid-infrared integrated band strengths for solid O(2), N(2)O and NO(2):N(2)O(4) mixtures

We present novel measurements of the refractive index, density and integrated band strengths of mid-infrared features of solid N(2)O at 16K and of NO(2) and N(2)O(4) in two frozen NO(2):N(2)O(4) mixtures deposited at 16 and 60K. The refractive index and density measurements were performed also for frozen O(2) deposited at 16K. In this case, the integrated band strength values could not be determined since O(2) is a homonuclear molecule and therefore its fundamental mode is not infrared active. The solid samples were analysed by infrared spectroscopy in the 8000/800cm(-1) range. The sample thickness was measured by the interference curve obtained using a He-Ne laser operating at 543nm. The refractive index at this laser wavelength was obtained, by numerical methods, from the measured amplitude of the interference curve. The density values were obtained using the Lorentz-Lorenz relation. Integrated band strength values were then obtained by a linear fit of the integrated band intensities plotted versus column density values. The astrophysical relevance of these novel measurements is briefly discussed.