OBSERVATION OF STRONG ELECTRONIC CORRELATION FOR HIGHLY EXCITED DOUBLE RYDBERG STATES OF YTTERBIUM

Using five-laser resonance excitation in combination with a method of sequential ionization by a pulsed and a constant electric field, we have observed the nearly pure spectra (the ion resonance background was greatly suppressed) for the highly excited double Rydberg states NLn'l (N greater than or similar to 40, N/n'greater than or similar to 0. 5 and L,1<4) of ytterbium in which the mutual penetration of the two excited wave functions is remarkable. Analysis of the spectra (relative cross section for different L states)has revealed the importance of the ''hybridization'' in the excited electron orbits which arises from the correlation of the two electrons in such highly excited states.