15min:

N. BOULOUFA, P. CACCIANI AND R. VETTER, Laboratoire Aimé Cotton (CNRS UPR3321), Campus d'Orsay, Bâtiment 505, 91405 Orsay, France.

We have studied the potential barrier in the B¹_u state of lithium dimers by use of a Doppler-free spectroscopy experiment in which a cw tunable laser beam crosses an effusive beam of lithium. Under these conditions, hundreds of wavenumbers have been measured to an accuracy of 10^-3 cm^-1. From broadened profiles corresponding to P, Q and R transitions for v^'=13, 14, 15 and 16, it is possible to describe the potential barrier of the B¹_u state, between 50 cm^-1 and 150 cm^-1 from its top. These results complement the ones obtained by use of Fourier transform spectroscopy with Doppler-broadened light sources. Theoretical interpretation is on the tracks.