  Traditionally, it has been assumed that electroluminescence (EL) in time
projection chambers was purely an excimer-based emission. This idea changed
when neutral bremsstrahlung (NBrS) was observed first in argon and subsequently
in xenon a few years ago. In this work we explore further the framework used to
explain these observations, presenting results for noble gas -based mixtures,
as well as mixtures including small fractions of a molecular additive
(`quencher'). Spectral content and yields are discussed in some cases of
contemporary interest, together with their pressure-scalings.
