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(DO NOT USE) Matrix Isolation/ Optical Constants of Ices Laboratory

The headshot image of Mark V. Vorobets

Mark V. Vorobets

Jul 22, 2019
Article

Contents

matrix

Members: Joe Roser

Objectives:

1. Measure mid-IR spectra of PAH neutrals, cations, and clusters to better constrain emitters of the Aromatic Infrared Bands, PAH-linked IR emission features seen throughout our Galaxy.

2. Measure optical constants of ammonia/water ices to provide fundamental data for reflectance modeling studies of outer Solar System bodies

Equipment:

Glass line: (10-8 Torr bkgd)

Matrix Isolation Chamber (Experiment)

  • Rotatable cryogenic stage (Tmin = 4 K with heat shield)
  • Crucible for evaporating molecules (Tmax = 750°C)
  • FTIR spectrometer (~15000–400 cm-1 / 0.67–25 µm)
  • H2 VUV discharge lamp (110–180 nm)

Associated Calculations

  • Estimate of monomer fraction of matrix-isolated PAHs
  • IR optical constants (Kramers-Kronig algorithm)   

Objective 1. Measure mid-IR spectra of PAH neutrals, cations, and clusters to better constrain emitters of the Aromatic Infrared Bands, PAH-linked IR emission features seen throughout our Galaxy.

Methodology:

  • Measure mid-IR spectra of PAH neutrals and clusters that are representative of the interstellar PAHs using IR Matrix Isolation Spectroscopy in argon matrix
  • Deduce cluster structural patterns from spectral features measured as a function of PAH concentration

Future projects: Large (40+ C) PAHs

Figure 2. Laboratory IR spectra of PAH clusters (Anthracene (left), pyrene (center), and benzene (right).•Blueshifted (blue box)
Figure 2. Laboratory IR spectra of PAH clusters (Anthracene (left), pyrene (center), and benzene (right).•Blueshifted (blue box) vs. redshifted(red box) CH out-of-plane bands are diagnostic of Tee vs. Parallel cluster stacking. (cf. Roser & Allamandola 2010; Roser et al. 2014; Roser & Ricca 2015)

Objective 2. Measure optical constants of ammonia/water ices to provide fundamental data for reflectance modeling studies of outer Solar System bodies

Application: Ammonia ice is important in the outer Solar System as a surface ice component and as a driver of cryovolcanism, recently confirmed to be occurring on Pluto.

Methodology:​ 

  • measure IR transmission spectra in the laboratory
  • derive optical constants from laboratory spectra using the well-known Kramers-Kronig algorithm in a Python code that utilizes an iterated optimization workflow to determine best-fit optical constants.

Future projects:

  • Measure optical constants of other ices and ice mixtures to provide fundamental data for reflectance modeling studies of outer Solar System bodies.
  • Determine optical constants of complex organic molecules (COM) of outer Solar System interest embedded in ices (nitrogen, methane, water)

Find our publications here.