SCATTERING EXPERIMENTS WITH SODIUM CLUSTERS - DIFFERENTIAL CROSS-SECTIONS AND CLASSICAL TRAJECTORY CALCULATIONS

Scattering of sodium clusters Na(n) (n = 3,8) with argon, neon and molecular nitrogen is investigated in a crossed molecular beam experiment. The clusters are scattered by a pulsed gas beam and subsequently ionized by a pulsed laser and detected in a time-of-flight mass spectrometer. Total differential cross sections for Na(n) + Ar, Ne and N2 (n = 3 - 8) are measured. The angularly resolved cross sections show a significant amount of energy transfer to the clusters in the collision process. Classical trajectory calculations are performed using an distance-dependant Huckel-type Hamiltonian with added pair potentials for the sodium-rare gas interaction. The results show good agreement with the measurements in the range of small impact parameters. It is observed that the different isomers of the clusters play an important role in the process. Discrete excitations are analyzed for Na3 and Na5. The shape of the measured angular distributions is explained from the superposition of rotational rainbows.