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.

Five different isotopologues of the benzoic acid dimer and a vibronic band located 57 cm(-1) above the electronic origin, which is assigned to the out-of-plane butterfly motion, are studied by rotationally resolved UV spectroscopy. From these measurements a ground-state structure with C(2h) symmetry is deduced, whereas the symmetry is lowered to C(s) in the S(1) state. The increase in the center-of-mass distance between the two monomers that is found on electronic excitation indicates a decrease in hydrogen-bond strength. The tunneling splittings in the S(0) and S(1) states are 1385.2+/-0.7 and 271.2+/-0.7 MHz, respectively, corresponding to an increase in barrier height by 7.2% on electronic excitation.

In this paper, hybrid air–water discharges were used to develop an optimal condition for providing a high level of water decomposition for hydrogen evolution. Electrical and optical phenomena accompanying the discharges were investigated along with feeding gases, flow rates and point-to-plane electrode gap distance. The experiments were primarily focused on the optical emission of the near UV range, providing a sufficient energy threshold for water dissociation and excitation. The OH(A 2Σ+ → X 2Π, Δν = 0) band optical emission intensity indicated the presence of plasma chemical reactions involving hydrogen formation. Despite the fact that energy input was high, the OH(A–X) optical emission was found to be negligible at the zero gap distance between the tip of the metal rod and water surface. In the gas atmosphere saturated with water vapour the OH(A–X) intensity was relatively high compared with the liquid and transient phases although the optical emission strongly depended on the flow rate and type of feeding gas. The gas phase was found to be more favourable because of less energy consumption in the cases of He and Ar carrier gases, and quenching mechanisms of oxygen in the N2 carrier gas atmosphere, preventing hydrogen from recombining with oxygen. In the gas phase the discharge was at a steady state, in contrast to the other phases, in which bubbles interrupted propagation of the plasma channel. Optical emission intensity of OH(A–X) band increased according to the flow rate or residence time of the He feeding gas. Nevertheless, a reciprocal tendency was acquired for N2 and Ar carrier gases. The peak value of OH(A–X) band optical emission intensity was observed near the water surface; however in the cases of Ar and N2 with a 0.5 SLM flow rate, it was shifted below the water surface. Rotational temperature was estimated to be in the range of 900–3600 K, according to the carrier gas and flow rate, which is sufficient for hydrogen production.

The rotationally resolved spectrum of the o-toluidine S(1)<-- S(0) origin was measured using laser induced fluorescence spectroscopy. From the resulting spectrum torsional barriers to internal rotation of the methyl group were derived, which resulted in S(0) state values of V(3) = 699 +/- 11 cm(-1) and V(6) = 64 +/- 11 cm(-1) with an effective rotational constant F of 5.38 +/- 0.04 cm(-1) while for the S(1) state the result was V(3) = 40.87 +/- 0.14 cm(-1) and V(6) = -16.8 +/- 0.8 cm(-1) with F = 5.086 +/- 0.001 cm(-1). The S(1) state structure was found to be severely distorted, with the methyl group making a 7.7 degrees degree angle with the benzene ring. Evidence of an excited state precessional motion of the methyl group was found.

The hydrogen bond structure of the p-cyanophenol-water cluster has been determined in the ground and first excited electronic state by rotationally resolved UV spectroscopy. The water molecule is trans-linearly bound to the hydroxy group of the p-cyanophenol moiety, with hydrogen bond distances considerably shorter in both electronic states than in the similar phenol-water cluster. The structure of the cluster has been elucidated by ab initio calculations at various levels of theory and compared to the experimental findings. The barriers to internal rotation of the water moiety were determined experimentally to be 275 and 183 cm(-1) for the ground and excited state, respectively. Hydrogen bond distances and the energy barrier to water torsion correlate with the pK(a) values of different substituted phenols for both electronic states.