Cluster intensity and velocity measurements in condensed flows

The objective of the present investigation has been to obtain further information concerning the condensation process in expanding flows. To this end, molecular beams formed from expansions of argon, nitrogen, carbon dioxide, nitric oxide, krypton, and a 10% krypton/argon mixture have been analyzed with a quadrupole mass spectrometer and a metastable velocity analyzer. By varying the energy of the ionizing electrons, it has been found that (1) at low source pressures, it can be assumed that the measured dimer intensity corresponds to that occurring in the beam; and (2) at high source pressures, i.e., where massive condensation has occurred, the dimer signal is largely dependent on the energy of the ionizing electrons. The variation of the source pressure at which massive condensation occurs with source diameter and temperature has been summarized for argon and nitrogen. (Modified author abstract)