Synchrotron radiation study on small binary molecular clusters: argon-water and carbon dioxide-water systems

Abstract

With synchrotron radiation we have carried out measurements of photoionization mass spectra and photoionization efficiency (PIE) curves for Ar-water and CO{sub 2}-water binary clusters produced in a supersonic jet. From the mass spectra obtained for the CO{sub 2}-H{sub 2}O system at 60 nm, we have detected the following cluster ions: ((H{sub 2}O){sub m}){sup +} (m = 1-5), ((H{sub 2}O)){sub m}H{sup +} (m = 1-5), ((CO{sub 2}){sub m}){sup +} (m = 1, 2), ((CO{sub 2}){sub m}(H{sub 2}O){sub n}){sup +} (m = 1; n = 1, 2), ((CO{sub 2}){sub m}(H{sub 2}O){sub n})H+ (m = 1; n = 1, 2). The PIE curves of producing several neat and mixed water cluster ions for the Ar-H{sub 2}O system show a monotonically increasing tendency in the 75-100-nm region, whereas the corresponding PIE curves obtained for the CO{sub 2}-H{sub 2}O system mostly show broad peaks due to photoionization of the CO{sub 2} site. From such differences between the two systems, it is suggested for the CO{sub 2}-H{sub 2}O system that intracluster charge transfer takes place from the CO{sub 2} site to the H{sub 2}O site before the formation of the neat and mixed water cluster ions. Evaporation processes of the neat and mixed water clusters aremore » discussed.« less