Cascade infrared thermal photon emission

TL;DR

This paper investigates how molecules and clusters emit infrared photons as they cool, revealing universal patterns and linear relationships in their energy and emission rates, regardless of specific vibrational details.

Contribution

It introduces a universal characterization of thermal infrared emission from excited molecules and clusters, showing linear dependence of emission rates on excitation energy.

Findings

Photon emission functions are universal across systems.

Emission rate constants vary linearly with excitation energy.

Results are exact for the derived linear dependence.

Abstract

The time development of the excitation energy of molecules and clusters cooling by emission of thermal vibrational infrared radiation has been studied. The energy distributions and the photon emission rates develop into near-universal functions that can be characterized with only a few parameters, irrespective of the precise vibrational spectra and oscillator strengths of the systems. The photon emission constant and emitted power averaged over all thermally populated states vary linearly with total excitation energy with a small offset. The time developments of ensemble internal energy distributions are calculated with respect to their first two moments. For the derived linear dependence of the emission rate constant, these results are exact.