Anionic hydrogen clusters as a source of diffuse interstellar bands (DIBs)

TL;DR

This study proposes that a family of seven anionic hydrogen clusters are stable in interstellar conditions and their spectral lines match observed diffuse interstellar bands, suggesting they could be key contributors.

Contribution

The paper introduces a new candidate family of anionic hydrogen clusters as sources of DIBs, supported by configuration interaction calculations and spectral analysis.

Findings

Seven hydrogen anionic clusters are stable at interstellar temperatures.

Spectral lines of these clusters match 25 observed DIBs within uncertainties.

Absorption bands originate from excitations to metastable states.

Abstract

The sources behind numerous key diffuse interstellar bands (DIBs) remain elusive, and thus evidence is presented here that a family of seven anionic hydrogen atomic clusters (H(-)2n+1, n = 1 to 7) are pertinent contributors. Configuration interaction calculations show hat these charge-induced dipole clusters are stable at temperatures characteristic of the interstellar medium, and emerge from the most abundant element in the Universe. The clusters' spectra yield 25 absorption optical lines that align with observed DIBs to within the computational uncertainties. The absorption bands are due to excitations from the ground states of the clusters to metastable states.