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The Mg 3pns (n =10-18) and 3pnd (n =9-40) doubly excited J =1 autoionizing states have been observed experimentally using an isolated-core excitation method with stepwise laser excitation.Linearly polarized laser light excites the 3pnd J = 1 and J =3 states, as well as the 3pns J = 1 states. Our previous study of the J =3 states enables the J =1 states in the 3pnd spectra to be identified.We have also calculated the spectra from a reaction matrix, and the agreement between theory and experiment is generally excellent. Differences between the J=1 and J=3 features are discussed and qualitatively explained in terms of semiclassical arguments. Additionally, energies of the 3sns 'So (n = 11 -22) Rydberg levels are reported.

The Mg 3pnd J =3 autoionizing spectra have been studied for n values ranging from 9 to 40, using an isolated-core excitation technique with ion detection. The measured spectra are found to be in generally excellent agreement with results from a calculated reaction matrix. The observed spectra exhibit strong interseries interactions between the 3pl/. nd;/2 and 3p&/2nd, series, and, for n 15, interferences between the amplitudes for excitation of the core electron to the 3P, /, and 3P3/2 ion states. Classifications of states for n «29 are tabulated. We discuss the difficulties in deducing autoionization rates for Mg from the experimental and theoretical data, the implications of which could have relevance to dielectronic recombination rate calculations.

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