Daniel Spangenberg

Structure and vibrations of phenol(H2O)7,8 studied by infrared-ultraviolet and ultraviolet-ultraviolet double-resonance spectroscopy and ab initio theory

The vibronic spectra of jet cooled phenol(H2O)7,8 clusters were analyzed with mass selective resonance enhanced two photon ionization (R2PI) and ultraviolet-ultraviolet spectral hole burning (UV-UV SHB). A double resonance technique with an infrared (IR) laser as burn laser (IR-UV SHB) was used to measure the intramolecular OH stretching vibrations of the mass- and isomer-selected clusters. Two isomers of phenol(H2O)7 and three isomers of phenol(H2O)8 could be distinguished via SHB and their IR spectra recorded. The red- or blueshift of the electronic origin relative to the phenol monomer gives valuable hints on the hydrogen bonding between phenol and the water moiety. All IR spectra contain four characteristic groups of OH stretching vibrations which give insight into the structure of the H bonded network. The ab initio calculations show that the minimum energy structures for phenol(H2O)7,8 are very similar to the corresponding water clusters which are based on regular (H2O)8 cubes. Comparison between ex...

The structure of phenol in the S1-state determined by high resolution UV-spectroscopy

Abstract The structure of phenol in the electronically excited S1-state has been examined by rotationally resolved UV-spectroscopy of different isotopomers of phenol. The geometry has been fit to the inertial parameters of 12 isotopomers, using different pseudo-Kraitchman fitting strategies. The resulting r0, rs, rm(1), and rm(2) structures, which differ in the amount of consideration of vibrational effects, will be compared among one another as well as to the results of published ab initio studies. The geometry of the -COH substructure has been determined separately for both electronic states by applying Kraitchman’s equations. Independent of the fitting strategy we found a shortening of the CO bond, an increase of the OH bond length and an expansion of the aromatic ring upon electronic excitation. The internal rotation of the hydroxy group causes line splittings that could be observed in the case of the OH species, but remained unresolved for all OD isotopomers. The S1-state lifetimes of the different isotopomers are shown to depend mainly on the presence of the OH function and depend less on the exchange of CH by CD. Thus, the OH stretching mode is most likely the dominant accepting mode, responsible for the rapid internal conversion in phenol.

Determination of the structures and barriers to hindered internal rotation of the phenol–methanol cluster in the S0 and S1 states

Abstract The rotationally resolved S 1 ←S 0 electronic spectrum of the hydrogen-bonded phenol–methanol cluster has been analyzed. Due to the internal rotation of the methyl group in the methanol moiety, the spectrum of the electronic origin of phenol–methanol is split into A and E subtorsional bands. From a perturbation analysis of the torsional–rotational structure of the electronic origin, the threefold barriers to internal rotation of the methyl group could be determined to be 170 cm −1 in the S 0 state and 150 cm −1 in the S 1 state. The perturbation analysis yielded the angle between the internal rotor axis and the inertial axes of the cluster, which allows the determination of the geometry of the hydrogen bond in both electronic states.

The S1 state geometry of phenol determined by simultaneous Franck–Condon and rotational constants fits

We describe a program for Franck–Condon simulations of dispersed fluorescence spectra obtained from excitation of single vibronic fundamental, overtone and combination levels. The S1 state geometry of phenol has been determined by a simultaneous fit of the geometry to the vibronic intensities and effective rotational constants in the harmonic limit based on ab initio force constants.

Structure and energetics of phenol(H2O)n, n⩽7: Quantum Monte Carlo calculations and double resonance experiments

Using a variety of methods phenol water clusters phenol(H2O)n, n⩽7, are investigated with a focus on phenol(H2O)5,6. A comprehensive search for low-energy isomers is conducted on a polarizable intermolecular potential energy surface. Zero-point energy contributions are calculated rigorously with the rigid-body quantum Monte Carlo method. The OH stretch vibrational spectra of the isomers are calculated using a local-mode model and compared with experimental isomer-selective IR–UV spectral hole burning (SHB) spectra. The topology of the clusters phenol(H2O)5,6 is shown in deviate from the corresponding pure water clusters.