EXPERIMENTAL-DETERMINATION OF THE DYNAMICS OF A MOLECULAR NUCLEAR WAVE-PACKET VIA THE SPECTRA OF SPONTANEOUS EMISSION

The dynamics of a wave packet in the nuclear degree of freedom of a sodium dimer have been studied via the time- and frequency-resolved spectrum of spontaneous emission. This technique allows one to track the nuclear wave packet dynamics in a single excited electronic state over a substantial fraction of its periodic trajectory. The quantum beats in the spectrum may be partially interpreted in terms of the classical-like evolution of an initially random distribution of internuclear separations. We observe the expansion and contraction of the wave packet that is characteristic of a quadrature squeezed state.