REMPI and IR-UV double resonance spectroscopy of 3-aminophenol·(NH3)1 cluster in the gas phase

The electronic and geometric structures of the cluster consisting of 3-aminophenol (3AP) and one ammonia molecule were investigated using resonance-enhanced multiphoton ionization and IR-UV double resonance spectroscopy in the gas phase. Between the cis and trans isomers found for the bare 3AP molecule, only trans isomer was found for 3AP·(NH3)1. It was found that complete quenching of the excited state of cis isomer, e.g. by conformer-specific excited state hydrogen transfer reaction, does not seem to occur, but that efficient conformational cooling drives the ground state population into the most stable trans isomer. The 0-0 band of the trans-3AP·(NH3)1 at 34 409 cm−1 is red-shifted by 68 cm−1 from that of the trans-3AP at 34 477 cm−1. The IR depletion spectrum shows that the OH stretching vibration (3296 cm−1) is red-shifted by 362 cm−1 from that of the bare molecule. The large red-shift in OH frequency, combined with MP2 calculation, reveals that the structure of the cluster is the one with the nitrogen atom of ammonia bound to the hydroxyl hydrogen of aminophenol.