Multiphoton ionisation of strontium creating Sr⁺and Sr²⁺

Abstract

Multiphoton ionisation of strontium atoms to Sr+ and Sr2+ has been investigated with a Nd-YAG laser ( lambda =10642 AA), its second, third and fourth harmonics and a tunable dye laser in a wavelength region around 5321 AA. The power dependence of the Sr+ and Sr2+ production has been obtained. The creation of Sr2+ is discussed with respect to two models: the simultaneous excitation and elimination of two electrons and a stepwise ionisation via Sr+.