Abstract
The cosmic unidentified infrared emission (UIE) band phenomenon is generally considered as indicative of free-flying polycyclic aromatic hydrocarbon molecules in space. However, a coherent explanation of emission spectral band patterns depending on astrophysical source is yet to be resolved under this attribution. Meanwhile astronomers have restored the alternative origin as due to amorphous carbon particles, but assigning spectral patterns to specific structural elements of particles is equally challenging. Here we report a physical principle in which inclusion of nonplanar structural defects in aromatic core molecular structures ( domains) induces spectral patterns typical of the phenomenon. We show that defects in model domains modulate the electronic-vibration coupling that activates the delocalized -electron contribution to aromatic vibrational modes. The modulation naturally disperses stretch modes in band patterns that readily resemble the UIE bands in the elusive range. The electron-vibration interaction mechanics governing the defect-induced band patterns underscores the importance of delocalization in the emergence of UIE bands. We discuss the global UIE band regularity of this range as compatible with an emission from the delocalized phase, as domains, confined in disordered carbon mixed-phase aggregates.
- Received 29 March 2017
DOI:https://doi.org/10.1103/PhysRevLett.119.171102
© 2017 American Physical Society
Physics Subject Headings (PhySH)
Synopsis
Explaining Mysterious Cosmic Emissions
Published 23 October 2017
A theoretical study shows how hydrocarbons with structural defects might produce unexplained peaks in the cosmic infrared spectrum.
See more in Physics