The $\lambda$6614 diffuse interstellar absorption band: evidence for internal excitation of the carrier

TL;DR

This study analyzes the $614$ diffuse interstellar band profiles to investigate how internal excitation of the carrier, mainly vibrational hot bands, influences the spectral shape, providing insights into the band formation mechanisms.

Contribution

It presents evidence linking the shape variations of the $614$ diffuse band to the internal excitation states of its carrier, emphasizing vibrational hot bands as a key factor.

Findings

Band shape differences are due to internal excitation levels.

Vibrational hot bands significantly influence spectral profiles.

Electronic excitation may also contribute to the band shape.

Abstract

An analysis of absorption profiles of the $\lambda$6614 diffuse interstellar band recorded along the lines-of-sight towards HD 179406 (20 Aql) and HD 147889 is described. The difference in band shape is attributed to the degree of internal excitation of the carrier, which is principally due to vibrational hot bands although an electronic component may also be present. The results are discussed with respect to other models of diffuse band spectral line shape.