Abstract: In a spectroscopic apparatus, a desolvated aerosol containing sample impurities to be analyzed is introduced into the center of a toroidal shaped plasma which is excited by an inductively coupled radio frequency power oscillator characterized by a single resonant circuit comprising an induction coil and its associated tuning capacitor, the plasma being produced by passing a gas stream along the axis of the induction coil. The single resonant circuit defined by the interconnection between the plate tank circuit and the grid tank circuit of the radio frequency power oscillator is such as to provide a common inductance for both circuits and to furnish power output and feedback for maintaining oscillation, whereby any detuning caused by introduction of the desolvated aerosol into the plasma does not affect the level of power transfer over a wide range.