Quantum confinement and carbon nanodots: A conceptual view for the origin of diffuse interstellar bands

TL;DR

This paper proposes a conceptual model where quantum confinement effects in carbon nanodots, modeled as nanodiamonds and amorphous carbon particles, could explain the energy transitions responsible for some diffuse interstellar bands, without identifying specific bands.

Contribution

It introduces a novel framework linking quantum confinement in carbon nanodots to DIBs, emphasizing particle size effects and exciton physics as potential explanations.

Findings

Particle size effects in nanodiamonds and a-C(:H) nanodots align with some DIB positions.

The model predicts single bands from most particle sizes and dual bands from some, depending on transitions.

Size-dependent quantum effects could be key to understanding the origin of certain DIBs.

Abstract

The nature of the Diffuse Interstellar Band (DIB) carriers is perhaps the most studied, longest standing, unresolved problem in astronomy. While four bands have been associated with the fullerene cation (C^+_60) the vast majority (> 550) remain unidentified. This works is an attempt to provide a conceptual framework for the typical energy transitions that are central to explaining the origin of DIBs, however, it does not make an association between these transitions and any particular DIBs. The effect of quantum confinement on excitons is used, including charge transfer excitons, to construct a generic basis for the electronic transitions that could, in principle, be coherent with the energies associated with DIBs. In this model the carriers are carbon nanodots (CNDs) modelled as nanodiamonds and a-C(:H) nanoparticles. These preliminary results seem to show that particle size dependent effects in nanodiamond and a-C(:H) CNDs could be consistent with the positions of, and intervals between, some of the DIBs. One particular strength of the model is that predicts single bands from the majority of single-size particles and, at most, two bands from some of these same carriers. In the latter case the two bands come from different transitions and may or may not inter-correlate, depending upon the local environment. This generic framework indicates that the size dependent fundamental transitions in CNDs could provide a viable scenario for the origin of some DIB-type bands. While this work does not identify a single DIB, it furnishes a conceptual view for the DIB origin, and suggests that a more refined exploration of quantum confinement size effects, and exciton physics within the astronomical domain might prove fruitful. This work also hints at the requirement for stable configurations for particular size domains in order to explain DIB wavelength stability.