General theory of light propagation and triplet generation for studies of spin dynamics and triplet dynamic nuclear polarisation

A general theory is presented describing the photo-excitation dynamics of transient, paramagnetic triplet states aromatic molecules including their absorption properties in a molecular host crystal when irradiated by pulsed laser beam. It applied to system pentacene doped naphthalene single crystal, where results highly non-equilibrium population intermediate electronic states. These can be addressed align proton spins at moderate experimental conditions using dynamic nuclear polarisation (DNP). The profile and resulting state distribution, which determined material parameters, leads corresponding profile. Measurements inhomogeneity spatially resolved neutron transmission confirm theory. theoretical model then allows extraction crucial parameters that enable quantitative investigations spin systems. For applications DNP with pentacene-doped crystals, maximum, homogeneity build-up rate are key factors, identification optimal depending on priorities placed these factors.