Conformational structures of jet-cooled acetaminophen-water clusters: a gas phase spectroscopic and computational study.

Jet-cooled acetaminophen (AAP)-water clusters, AAP-(HO), were investigated by mass-selected resonant two-photon ionization (R2PI), ultraviolet-ultraviolet hole-burning (UV-UV HB), infrared-dip (IR-dip), and infrared-ultraviolet hole-burning (IR-UV HB) spectroscopy. Each syn- and anti-AAP rotamer has three distinctive binding sites (-OH, >CO, and >NH) for a water molecule, thus 6 different AAP-(HO) conformers are expected to exist in the molecular beam. The origin bands of the AAP(OH)-(HO) and AAP(CO)-(HO) conformers (including their syn- and anti-conformers) in the R2PI spectrum are shifted to red and blue compared to those of the AAP monomer, respectively.