Infrared complex refractive index of N-containing astrophysical ices free of water processed by cosmic-ray simulated in laboratory

Rocha, W. R. M.; Pilling, S.; Domaracka, A.; Rothard, H.; Boduch, P.

doi:10.1016/j.saa.2019.117826

Cited by 4 publications

(2 citation statements)

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“…Likewise, IR spectra of binary ice mixtures and refractive indexes of pure ices can be found on the web page of the Cosmic Ice Laboratory 9 from NASA (e.g., Moore et al 2010;Knez et al 2012;Gerakines & Hudson 2020) and at Databases of the Astrophysics & Astrochemistry Laboratory 10 , which contains measurements by Hudgins et al (1993). A database of refractive indices of ice samples irradiated by heavy ions is also available on the Laboratório de Astroquímica e Astrobiologia da Univap (LASA) webpage 11 with calculations performed by Rocha & Pilling (2014), Pilling (2018), andRocha et al (2020). Infrared refractive indices of CO and CO 2 ices are available from the Experimental Astrophysics Laboratory on the Catania Astrophysical Observatory website 12 .…”

Section: Introductionmentioning

confidence: 99%

LIDA: The Leiden Ice Database for Astrochemistry

Rocha

Rachid

Olsthoorn

et al. 2022

A&A

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Context. High-quality vibrational spectra of solid-phase molecules in ice mixtures and for temperatures of astrophysical relevance are needed to interpret infrared observations toward protostars and background stars. Such data are collected worldwide by several laboratory groups in support of existing and upcoming astronomical observations. Over the last 25 years, the Laboratory for Astrophysics at Leiden Observatory has provided more than 1100 (high-resolution) spectra of diverse ice samples. Aims. In time with the recent launch of the James Webb Space Telescope, we have fully upgraded the Leiden Ice Database for Astrochemistry (LIDA) adding recently measured spectra. The goal of this paper is to describe what options exist regarding accessing and working with a large collection of infrared (IR) spectra, and the ultraviolet-visible (UV/vis) to the mid-infrared refractive index of H 2 O ice. This also includes astronomy-oriented online tools to support the interpretation of IR ice observations. Methods. This ice database is based on open-source Python software, such as Flask and Bokeh, used to generate the web pages and graph visualization, respectively. Structured Query Language (SQL) is used for searching ice analogs within the database and Jmol allows for three-dimensional molecule visualization. The database provides the vibrational modes of molecules known and expected to exist as ice in space. These modes are characterized using density functional theory with the ORCA software. The IR data in the database are recorded via transmission spectroscopy of ice films condensed on cryogenic substrates. The real UV/vis refractive indices of H 2 O ice are derived from interference fringes created from the simultaneous use of a monochromatic HeNe laser beam and a broadband Xe-arc lamp, whereas the real and imaginary mid-IR values are theoretically calculated. LIDA not only provides information on fundamental ice properties, but it also offers online tools. The first tool, SPECFY, is directly linked to the data in the database to create a synthetic spectrum of ices towards protostars. The second tool allows the uploading of external files and the calculation of mid-infrared refractive index values.Results. LIDA provides an open-access and user-friendly platform to search, download, and visualize experimental data of astrophysically relevant molecules in the solid phase. It also provides the means to support astronomical observations; in particular, those that will be obtained with the James Webb Space Telescope. As an example, we analysed the Infrared Space Observatory spectrum of the protostar AFGL 989 using the resources available in LIDA and derived the column densities of H 2 O, CO and CO 2 ices.

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Section: Introductionmentioning

confidence: 99%

LIDA: The Leiden Ice Database for Astrochemistry

Rocha

Rachid

Olsthoorn

et al. 2022

A&A

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“…There is also a need for mid-IR refractive indices of ammonia and ammonia-containing compounds. In some astrophysical sources and in solar system sources such as Iapetus or Dione, a 2.97 μm band tentatively assigned to ammonia might become more easily discernible with the high spectral resolution and signal precision attainable with JWST, even in cases where the contribution of H 2 O is strong (e.g., Clark et al 2008Clark et al , 2012Rocha et al 2020). In addition, observations to be made by JWSTʼs Mid-Infrared Instrument (MIRI) will provide mid-IR spectra of astrophysical environments with molecular ices containing ammonia (e.g., Milam et al 2016).…”

Section: Introductionmentioning

confidence: 99%

The Infrared Complex Refractive Index of Amorphous Ammonia Ice at 40 K (1.43–22.73 μm) and Its Relevance to Outer Solar System Bodies

Roser¹,

Ricca²,

Cartwright³

et al. 2021

Planet. Sci. J.

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A near-IR absorption band at 2.2 μm linked to ammonia-containing ice has been detected on icy bodies throughout the solar system and appears in the extensive volume of data for Pluto and Charon returned by New Horizons. This band is an important clue for understanding the abundance of ammonia and ammoniated compounds on the surface of outer solar system bodies and requires new laboratory data for its full analysis. To satisfy this data need, the complex refractive index of amorphous ammonia ice was calculated from experimental infrared transmission spectra with ice deposition and measurements conducted at 40 K, a characteristic surface temperature for outer solar system bodies. The measured imaginary part of the complex refractive index and associated band strength calculations are generally larger than prior published values for amorphous ammonia ice at 30 K. The complex refractive index for amorphous ammonia at 40 K computed in the mid-infrared region (2.5–22.73 μm) will also be valuable for interpreting observations of both solar system and astrophysical sources anticipated with the Near InfraRed Spectrograph and Mid-Infrared Instrument on the James Webb Space Telescope.

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Fitting infrared ice spectra with genetic modelling algorithms

Rocha

Perotti

Kristensen

et al. 2021

A&A

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Context. A variety of laboratory ice spectra simulating different chemical environments, ice morphologies, and thermal and energetic processing are needed in order to provide an accurate interpretation of the infrared spectra of protostars. To decipher the combination of laboratory data that best fits the observations, an automated, statistics-based computational approach is necessary. Aims. We aim to introduce a new approach, based on evolutionary algorithms, to searching for molecules in ice mantles via spectral decomposition of infrared observational data with laboratory ice spectra. Methods. We introduce a publicly available and open-source fitting tool called ENIIGMA (dEcompositioN of Infrared Ice features using Genetic Modelling Algorithms). The tool has dedicated Python functions to carry out continuum determination of the protostellar spectra, silicate extraction, spectral decomposition, and statistical analysis to calculate confidence intervals and quantify degeneracy. We conducted fully blind and non-blind tests with known ice samples and constructed mixtures in order to asses the code. Additionally, we performed a complete analysis of the Elias 29 spectrum and compared our findings with previous results from the literature.Results. The ENIIGMA fitting tool can identify the correct ice samples and their fractions in all checks with known samples tested in this paper. In the cases where Gaussian noise was added to the experimental data, more robust genetic operators and more iterations became necessary. Concerning the Elias 29 spectrum, the broad spectral range between 2.5 and 20 µm was successfully decomposed after continuum determination and silicate extraction. This analysis allowed the identification of different molecules in the ice mantle, including a tentative detection of CH 3 CH 2 OH. Conclusions. The ENIIGMA is a toolbox for spectroscopy analysis of infrared spectra that is well-timed with the launch of the James Webb Space Telescope. Additionally, it allows different chemical environments and irradiation fields to be explored, allowing the user to correctly interpret astronomical observations.

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Infrared complex refractive index of N-containing astrophysical ices free of water processed by cosmic-ray simulated in laboratory

Cited by 4 publications

References 59 publications

LIDA: The Leiden Ice Database for Astrochemistry

LIDA: The Leiden Ice Database for Astrochemistry

The Infrared Complex Refractive Index of Amorphous Ammonia Ice at 40 K (1.43–22.73 μm) and Its Relevance to Outer Solar System Bodies

Fitting infrared ice spectra with genetic modelling algorithms

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