Thermal fluctuations and nanoscale effects in the nucleation of carbonaceous dust grains

TL;DR

This paper models how thermal fluctuations and nanoscale effects influence the nucleation rates of carbonaceous dust grains, revealing that these factors significantly alter cluster stability and nucleation, with implications for astrophysical dust formation.

Contribution

It introduces a Monte Carlo model incorporating thermal fluctuations and nanoscale effects to accurately predict nucleation rates of carbonaceous dust.

Findings

Thermal fluctuations and nanoscale effects significantly impact cluster stability.

Nucleation rates are faster when considering these effects.

Gas composition influences nucleation rates beyond partial pressure effects.

Abstract

We investigate the role of thermal fluctuations and of the finite number of monomers in small clusters of carbon atoms on the nucleation rate of carbonaceous grains. Thermal fluctuations are due to the quantized nature of the energy exchanges between the clusters, the gas, and the radiation field. Nanoscale effects modify the spontaneous detachment of monomers due to the finite amount of internal energy contained in small clusters. We find that both corrections have a big impact on the stability of the clusters and on the rate of nucleation. We implement our model within a Monte Carlo code to derive the new stability conditions for clusters as well as nucleation rates. Due to computing limitations, we can explore the consequences of this approach only at high temperatures, at which particle interactions are not much less frequent than photon interactions. We found that the combined effect of the detachment correction and the temperature fluctuations produces faster nucleation. We also found that the nucleation rate depends on the composition of the gas and not only on the partial pressure of the compound that condensates into grains. This is a unique result of this model that can be used to prove or disprove it.