Infrared Spectroscopy of Phenol-(H_2O)_(n 10): Structural Strains in Hydrogen Bond Networksof Neutral Water Clusters

摘要

To investigate hydrogen bond network structures of tens of water molecules, we report infrared spectra ofmoderately size (n)-selected phenol-(H_2O)_n (～10 ≤n≤～50),which have essentially the same networkstructures as (H_2O)_(n+1). The phenyl group in phenol-(H_2O)_n allows us to apply photoionization-based sizeselection and infrared-ultraviolet double resonance spectroscopy. The spectra show a clear low-frequencyshift of the free OH stretching band with increasing n. Detailed analyses with density functional theorycalculations indicate that this shift is accounted for by the hydrogen bond network development from highlystrained ones in the small (n < ～10) clusters to more relaxed ones in the larger clusters, in addition to thecooperativity of hydrogen bonds.