| Abstract
| - Reaction products in clusters containing an alkali metal atom (M = Na, K, and Cs) and methyl propiolate(MP) molecules have been examined from results of photoionization efficiency (PIE) curve measurements.Two distinct humps were commonly observed in the PIE curves of Cs(MP)n for n ≥ 3, whereas a relativelysmooth curve was obtained for n = 2. In the photoionization mass spectra of M(MP)n, an intensity anomalyat n = 3 was commonly observed as reported in the previous paper, which was due to a cyclotrimerizationreaction producing a benzene derivative (trimethyl benzenetricarboxylate, BT). From the results of quantumchemical calculations for reacted and unreacted isomers, these two humps originate from two isomers withdifferent ionization thresholds; the lower threshold is ascribed to a solvation-type isomer, Cs(MP)3, and thehigher value comes from a reacted isomer composed of a cesium atom and a BT molecule. From the relativeintensity of two isomers, the intracluster cyclotrimerization reaction producing BT is found to proceed efficientlyin the present M−MP clusters.
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