The effect of a radiation field on excitation and ionisation in non-LTE high energy density plasmas

In this paper we consider the direct effect of an ambient radiation field on the state of excitation and ionisation in a non-LTE high energy density plasma. We review both narrow-band and broad-band pumping and look at the theory that has been developed and the experiments performed using high-power lasers and pulsed-power devices and (potentially) X-ray free-electron lasers to investigate this effect.