Laserspectroscopic Investigations in the Configuration 5d6s6p of Lu I

The classification of the lower levels of Lu I is mainly based on the pioneer work of Meggers and Scribner [1] and Klinkenberg [2 ] . In a recent investigation Verges and Wyart [3] observed 155 emission lines in the infrared region of 1 — 3.7/<m. By means of Fourier transform spectroscopy they measured the magnetic and electric hyperfine constants of the combining levels of 40 lines for the isotope Lu1 '5. With these values it was possible for them to revise and extend the level scheme. In this way the term classification of the configurations 5d26s and 5d6s6p could be completed. Measurements of hyperfine constants of energy levels are very useful for a detailed study of coupling properties within a given configuration or of possible interaction with other configurations of the same parity. Complementary information for the classification of levels is given by the determination of lifetimes, because electric dipole transition probabilities depend on the coupling properties and on the radial integrals between configurations of different parity. In the case of the 5d6s6p configuration of Lu I the lifetimes of the lower levels at about 20 000 cm 1 (Fi g. 1) should mainly be due to transitions to the levels 2D.j/-) and 2D,-( o (1994 cm 1 ) of the ground state configuration 5d6s2. Because of the J.E3-depcndence of electric dipole transition probabilities the transitions to levels of the configuration 5d26s which lie above 18 851 cm"1 should be negligible. As most of the lower levels of the configuration 5d6s6p belong to the quartet system in the LS cou-