Laser-microwave spectroscopy of singlet Mg I atoms in S,P,D,F,G Rydberg state

For the first time the energy level positions of Mg I atoms have been measured with high accuracy by means of laser-microwave spectroscopy in the 79-234 GHz frequency range. The new measurements cover the range of principal quantum number n=25-40 in L=0-4 Rydberg states. Using our and optical measured frequencies the quantum defect constants for these states are obtained. The description of our spectrometer, measurement technique and results are presented.