Articles you may be interested inRotational analysis and tunnel splittings of the intermolecular vibrations of the phenol-water complex by high resolution UV spectroscopy J. Chem. Phys. 108, 4496 (1998); 10.1063/1.475861 Infrared spectroscopy of OH stretching vibrations of hydrogenbonded tropolone(H2O) n (n=1-3) and tropolone (CH3OH) n (n=1 and 2) clusters

Inertial axis reorientation in the S 1←S 0 electronic transition of 2pyridone. A rotational Duschinsky effect. Structural and dynamical consequences J. Chem. Phys. 95, 8732 (1991); 10.1063/1.461209 Molecular dynamics study of rotational reorientation of tryptophan and several indoles in water J. Chem. Phys. 94, 3857 (1991); 10.1063/1.460661 The S 1-S 0 transition of indole and Ndeuterated indole: Spectroscopy and picosecond dynamics in the excited state J. Chem. Phys. 91, 6013 (1989); 10.1063/1.457418The rotationally resolved electronic spectrum of indole in the gas phase Rotationally resolved laser induced fluorescence excitation spectra of the S 1 ( 1 L b )←S 0 origin bands of indole, indazole, and benzimidazole have been measured. From these spectra, the rotational constants in both electronic states have been determined. The spectra of all three molecules exhibit ''anomalous'' rotational line intensities. These intensity perturbations are a result of the reorientation, upon electronic excitation, of the inertial axes of the molecule. Intensity analysis of the rotational lines yielded information about the inertial axis reorientation, and the direction of the transition moment vector for each molecule.

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High resolution ultraviolet spectroscopy has been used to investigate the rotationally resolved excitation spectrum of the first singlet-singlet transition in the benzoic acid dimer. The measured spectrum consists of two overlapping components. The corresponding lines in the two components are shown to originate in different levels of the ground state potential separated by a tunneling splitting produced by concerted proton exchange between the two subunits forming the dimer. The frequency separation between the two components is equal to the difference between the tunneling splittings in the ground and the excited electronic state. This frequency separation is found to be 1107Ϯ7 MHz. From the analysis, it is estimated that the barrier for proton tunneling changes by about 20% upon electronic excitation. The structure of the dimer in the ground state is determined to be linear, while in the excited S 1 state it is slightly bent (3.4°Ϯ1.7°).

The conformational space of tryptamine has been thoroughly investigated using rotationally resolved laser-induced fluorescence spectroscopy. Six conformers could be identified on the basis of the inertial parameters of several deuterated isotopomers. Upon attaching a single water molecule, the conformational space collapses into a single conformer. For the hydrogen-bonded water cluster, this conformer is identified unambiguously as tryptamine A. In the complex, the water molecule acts as proton donor with respect to the amino group. An additional interaction with one of the aromatic C-H bonds selectively stabilizes the observed conformer more than all other conformers. Ab initio calculations confirm much larger energy differences between the conformers of the water complex than between those of the monomers.

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It is shown that a new procedure, based on genetic algorithms ͑GA's͒, can be used for direct determination of molecular constants, in particular rotational constants, from rovibronic spectra. This new approach only requires an estimate of the acceptable range of the parameters. The power of the method is demonstrated on the rotationally resolved fluorescence spectra of indole, indazole, benzimidazole, and 4-aminobenzonitril. A rigid asymmetric rotor Hamiltonian is used to calculate the theoretical spectra. The GA matches the generated spectra with an experimental spectrum with the use of a new method for spectra comparison. This spectra comparison function is able to deal with frequency shifts which are caused by ͑small͒ changes in the rotational constants and it yields better results in comparison with traditional spectra comparison methods, like RMS. In addition, the robustness of the method is tested.

The structures of the van der Waals bonded complexes of phenol with one and two argon atoms have been determined using rotationally resolved electronic spectroscopy of the S(1)<--S(0) transition. The experimentally determined structural parameters were compared to the results of quantum chemical calculations that are capable of properly describing dispersive interactions in the clusters. It was found that both complexes have pi-bound configurations, with the phenol-Ar(2) complex adopting a symmetric (1mid R:1) structure. The distances of the argon atoms to the aromatic plane in the electronic ground state of the n=1 and n=2 clusters are 353 and 355 pm, respectively. Resonance-enhanced multiphoton ionization spectroscopy was used to measure intermolecular vibrational frequencies in the S(1) state and Franck-Condon simulations were performed to confirm the structure of the phenol-Ar(2) cluster. These were found to be in excellent agreement with the (1mid R:1) configuration.