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Ionization-Induced Solvent Migration in Acetanilide-Methanol Clusters Inferred from Isomer-Selective Infrared Spectroscopy



We present the resonance-enhanced multiphoton ionization, infrared-ultraviolet hole burning (IR-UV HB), and IR dip spectra of the trans-acetanilide–methanol (AA–MeOH) cluster in the S0, S1, and cationic ground state (D0) in a supersonic jet. The IR-UV HB spectra demonstrate the co-existence of two isomers in S0,1, in which MeOH binds either to the NH or the CO site of the peptide linkage in AA, denoted as AA(NH)–MeOH and AA(CO)–MeOH. When AA(CO)–MeOH is selectively ionized, its IR spectrum in D0 is the same as that measured for AA+(NH)–MeOH. Thus, photoionization of AA(CO)–MeOH induces migration of MeOH from the CO to the NH site with 100% yield.