Study of protonated methanol cluster ions under thermal conditions

Abstract

Size-dependent intracluster reactions within the methanol cluster system are studied using a fast flow reactor operated under thermal conditions. At low temperature, large protonated methanol cluster ions (CH 3OH) n H + ( n up to 24) are produced for the first time under thermal conditions. Two mixed cluster ion series of (CH 3OH)) n (CH 3OCH 3)H + and (CH 3OH) n (H 2O)H + are also observed. Interestingly, the cluster ion patterns are found to be greatly influenced by the degree of solvation, due to several size specific intracluster ion—molecule reactions. The mixed cluster ions (CH 3OH) n (CH 3OCH 3)H + are observed only for the small clusters ( n⩽5) while the mixed cluster ions (CH 3OH) n (H 2O)H + are seen only for the large ones ( n⩾7). The work reported herein is particularly significant in that it demonstrates under thermal conditions, the influence of the degree of solvation on the course of intracluster ion—molecule reactions. Moreover, these new findings further support what is becoming a general observation concerning the role of the number of bonding sites in affecting the chemical nature of the ion core in mixed clusters.