Knowledge Bank

When ionizing phenol-ammonia clusters in a supersonic jet expansion between 276 and 285 nm under 1-color 2-photon conditions, the proton transfer $(NH3)1-4H+$ ion yields depend distinctly on the excitation wavelength. The $S1$-vibronic spectra measured via the phenol $(NH3)1-4\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ - and the $(NH3)1-4H+$ ion yields show a 1:1 correspondence with only small or none sign of phenol $(NH3)n+1S1$ - bands in the $(NH3)nH+$ -spectra (i. e., little fragmentation after proton transfer). The proton transfer yield spectra allow high quality measurements of the $S1$ vibronic resonances at $n>3$, where the phenol $(NH3)n$ spectra themselves show little structure. The data show enhanced $(NH3)1H+$ ion yield after excitation of the phenol $(NH3)1S1$ - electronic origin demonstrating proton transfer even in the n=1 cluster at sufficient phenol $(NH3)1+$ ion excess energy ($\ge 8000cm-1$ at 2-photon absorption). Underlying the sharp phenol $(NH3)nS1$ - bands we observe broad spectral features which extend to the red of the phenol $(NH3)n$ spectra and resemble somewhat to the electronic spectrum of the phenolatanion $PhO\ast$. We very tentatively assign the spectrum to excitation to the $PhO\ast H+(NH3)n$ charge transfer state. Structure and dynamics of phenol $(NH3)2$ and phenol-$d1-(ND3)2$ are discussed in detail based on the observed $S1$ intermolecular vibrations and tunnel splittings in comparison to results from ab initio calculations.