Observation of magnetic-field-enhanced excitation and ionization in the plume of KrF-laser-ablated magnesium

The influence of a magnetic field on the plume produced by KrF-laser ablation of magnesium in vacuum has been investigated using time-integrated photography, streak photography, spectroscopy and charge probes. Line emission spectra in the 200–600 nm interval and effective stream velocities for the plume obtained from the spatiotemporal emission from specific neutral and ion lines are reported. Time of flight velocities are also deduced from measurements using simple charge-collector probes. Changes in the plume structure and dynamics, and enhanced emission and ionization are observed in the presence of the field. A qualitative explanation of the results is given in terms of a magnetohydrodynamic model.