  Muon spin spectroscopy and in particular the avoid level crossing (ALC)
technique is a sensitive probe of electron spin relaxation (eSR) in organic
semiconductors. In complex ALC spectra, eSR can be challenging to extract, as
it requires the modelling of overlapping ALCs, where covariance between
parameters can result in significant uncertainties. Here we demonstrate a
general method to extract eSR rate, which is independent on the number of ALCs
resonances present, whether they overlap or not, and what the muonium hyperfine
(isotropic and anisotropic) parameters are. This can then be used to extract an
accurate value for eSR rate and as guidance for undertaking experiments
efficiently
