- Names
-
- C. Ennis
- R. Auchettl
- M. Ruzi
- E. G. Robertson
- Title
- Infrared characterisation of acetonitrile and propionitrile aerosols under Titan's atmospheric conditions
- Abstract
- Pure, crystalline acetonitrile ($CH_3CN$) and propionitrile ($CH_3CH_2CN$) particles were formed in a collisional cooling cell allowing for infrared (IR) signatures to be compiled from 50 to 5000 cm${-1}$. The cell temperature and pressure conditions were controlled to simulate Titan’s lower atmosphere (80–130 K and 1–100 mbar), allowing for the comparison of laboratory data to the spectra obtained from the Cassini–Huygens mission. The far-IR features confirmed the morphology of $CH_3CN$ aerosols as the metastable $\beta$-phase (monoclinic) ice, however, a specific crystalline phase for $CH_3CH_2CN$ could not be verified. Mie theory and the literature complex refractive indices enabled of the experimental spectra to be modelled. The procedure yielded size distributions for $CH_3CN$ (55–140 nm) and $CH_3CH_2CN$ (140–160 nm) particles. Effective kinetic profiles, tracing the evolution of aerosol band intensities, showed that condensation of $CH_3CH_2CN$ proceeded at twice the rate of $CH_3CN$ aerosols. In addition, the rate of $CH_3CH_2CN$ aerosol depletion via lateral diffusion of the particles from the interrogation volume was approximately 50% faster than that of $CH_3CN$. The far-IR spectra recorded for both nitrile aerosols did not display absorption profiles that could be attributed to the unassigned 220 cm${-1}$ feature, which has been observed to fluctuate seasonally in the spectra obtained from Titan’s atmosphere.
- Keywords
- spectroscopy, absorbance spectra, data analysis, band position, band vibration mode, mid-IR, far-IR, amorphous, crystalline, aerosols, molecular solid, nitrile, CH3CN, CH3CH2CN, acetonitrile, propionitrile, Titan
- Content
- spectral data, band list data
- Year
- 2017
- Journal
- Physical Chemistry Chemical Physics
- Volume
- 19
- Number
- 4
- Pages
- 2915 - 2925
- Pages number
- 11
- Document type
- article
- Publication state
- published
- Doi
- 10.1039/C6CP08110J
- Identifiers
-
- bibcode: 2017PCCP...19.2915E