Diffuse Interstellar Bands: A Comprehensive Laboratory Study

TL;DR

This comprehensive laboratory study investigates potential molecules responsible for diffuse interstellar bands, implicating stable organic molecules, grains, and pyridine, and correlates laboratory spectra with astronomical observations to identify likely carriers.

Contribution

It provides experimental data linking specific organic molecules and grains to diffuse interstellar bands, advancing understanding of their molecular carriers.

Findings

MgTBP and H2TBP are implicated as stable organic carriers.

The UV bump at 2175 Å is explained by pyridine in grains.

Laboratory spectra match astronomical fluorescence data.

Abstract

As a result of the search for the identity of the chromophores responsible for producing the diffuse interstellar bands, a comprehensive exposition of experimental data is presented, which implicates the following molecules- 1. The extremely stable organic molecules, magnesium tetrabenzoporphyrin (MgTBP) and H2TBP. 2. A paraffin matrix (referred to as grains) containing TBPs. 3. A low concentration of pyridine (also within the grains), whose transmission window at 2175 Angstroms, accounts for the ubiquitous UV bump. The blue emission spectra associated with the central star, HD44179, of the Red Rectangle displays the fluorescence excitation spectra of bare MgTBP. This unique spectrum matches the low temperature lab data of MgTBP in the vapor phase. An effective grain temperature of 2.728 K (plus or minus 0.008) was deduced, based on MgTBPs lowest measured vibrational state of 341 GHz.