Measurement of pick-up cross-sections of He-4 clusters: polar versus non-polar molecules

Pick-up cross-sections of free large He-4 clusters formed in free jet expan sions have been measured to determine the influence of the molecular proper ties of target molecules in the capture process. The pick-up cross-section depends strongly on the dipole moment of the molecule. For non-polar molecu les, earlier measurements of pick-up cross-sections ranging from 2000 to 43 00 A(2) were confirmed; for polar systems, however, cross-sections between 6400 and 8100 Angstrom(2) were observed. In both cases a linear cross-secti on versus mass dependence is observed.