Diffuse interstellar bands: A comprehensive laboratory study

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 H 2 TBP. 2. A paraffin matrix (referred to as "grains") containing TBPs. 3. A low concentration of pyridine (also within the grains), whose transmission window at 2175Å, 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 (+/-0.008) was deduced, based on MgTBP's lowest measured vibrational state of 341 GHz.

Cosmic biology in perspective

“…From the 1930s onwards observed spectra of reddened stars have shown a large number of unidentified diffuse interstellar bands (DIBs) extending over visual and near IR wavelengths (Herbig 1995). Complex organic molecules, including even molecules related to chlorophyll, have been proposed but conclusive identification of a specific carrier has remained elusive (Johnson 2006). Two spectral lines at 9577 Å and 9632 Å match a singly charged fullerine C + 60 (Campbell et al 2015), although such an identification of only 2 out of some 400 similar lines can be questioned.…”

Electronic Transitions Responsible for C60+ Diffuse Interstellar Bands

“…Diffuse interstellar bands (DIBs) are spectroscopic features caused by the absorption of light passing through the interstellar medium (ISM) . About 500 DIBs mostly in the visible and infrared regions have been observed, but the origin of these bands is not clear. − DIBs are substructured and therefore most likely caused by the molecules in the gas phase rather than by interstellar dust and grains. , Polycyclic aromatic hydrocarbons (PAHs) and fullerenes are considered to be the main candidates for the origin of DIBs as these molecules can survive under extreme interstellar conditions − and because of the abundance of interstellar spectral features attributed to carbon-rich polyatomic molecules. − Despite significant efforts, no specific PAHs have been identified as the origin of DIBs .…”

Interstellar Grains: 50 Years On

“…A possible candidate in this category was proposed by F.M. Johnson in the form of magnesium tetrabenzo porphyrine (Johnson, 2006).…”