EFFECTIVE ABSOLUTE RATE-CONSTANT FOR THE FORMATION OF NEGATIVELY-CHARGED CO2 CLUSTER IONS BY ELECTRON-TRANSFER FROM STATE-SELECTED RYDBERG ATOMS

We have studied electron transfer from state-selected Ar**(nd) Rydberg atoms to (CO2)m clusters for 12 less-than-or-equal-to 48. The relative rate constant for the total negative ion formation reaches its maximum for n = 21 and decreases towards lower and higher n. From an accurate study of Penning ionization of nozzle beams with and without cluster formation we were able to derive the condensed fraction in our (CO2)m cluster beam and from a statistical analysis of cluster distributions we obtain an estimate for the absolute value of the effective rate constant for the total negative ion formation, which amounts to (4.5 +/- 3).10(-8) cm3/s for Ar**(21 d).