Stochastic Liouville equations for hydrogen-bonding fluctuations and their signatures in two-dimensional vibrational spectroscopy of water

The effects of hydrogen-bond forming and breaking kinetics on the linear and coherent third-order infrared spectra of the OH stretch of HOD in D2O are described by Markovian, not necessarily Gaussian, fluctuations and simulated using the stochastic Liouville equations. Slow (0.5 ps) fluctuations are represented by a collective electrostatic coordinate, whereas fast (<100 fs) frequency fluctuations are described using either a second collective electrostatic coordinate or a four-state jump (FSJ) model for hydrogen-bonding configurations. Parameters for both models were obtained using a 1-ns molecular-dynamics trajectory calculated using the TIP4P force field combined with an electrostatic ab initio map. The asymmetry of the photon-echo spectra (larger linewidth on the blue side than on the red side) predicted by the FSJ is in better agreement with recent experiments.     

Inter- and intra-molecular radiationless transitions of NO2 at around 454.6 nm

The continuum emission of NO₂ was investigated on the basis of time-resolved excitation and fluorescence spectra. The analysis of the observed spectra indicated the coexistence of inter- and intra-molecular relaxation processes of NO₂. The continuum emission, the relative intensity of which at longer wavelengths increases more drastically as time goes on after excitation (2–6 μs), was concluded to originate predominantly from molecular collisions in a stepwise deactivation process. A fast component of the continuum emission, with a relative intensity with respect to the discrete band (I_C/I_D) independent of time and of NO₂ pressure, appeared in collision-free conditions (<20 ns, 15 mTorr), and it was concluded to originate from radiationless transitions in isolated molecules.     

Nucleophilic character of alkyl radicals—XII : Mechanism and new syntheses in the oxidation of alcohols by peroxydisulphate

The debated mechanism of the oxidation of alcohols by peroxydisulphate was investigated by trapping the nucleophilic carbon-centered free-radical intermediates by protonated quinoline. The oxidation of t-butanol, 1-hexanol, 2,3-dimethyl-2-butanol and ethylene glycol in the presence of silver salt takes place via alkoxy radical intermediates arising from the interaction R-OH + Ag²⁺ → R-O^· + Ag⁺ + H⁺; it gives rise to new interesting selective synthetic processes. In the absence of silver salt the hydrogen abstraction from CH bonds is the main reaction.     

Isomerization of cyclooctatetraene oxide in the reaction with organometallic reagents : Possible involvement of homotropylium cation intermediate

The reaction of cyclooctatetraene oxide (1) with several organometallic reagents and metal salts were investigated with reference to skeletal change of the ring. LAH causes ring cleavage to yield octa-2,4,6-trienal along with the formation of cycloocta-3,5-dienol. Ethylmagnesium bromide and triethylaluminum afford ethyl(cyclohepta-2,4,6-trienyl)methanol in good yields, but the addition of HMPA in the Grignard reaction results in reduction of the reactivity and formation of the isomerized cyclic trienone. A similar medium effect by HMPA or solvent is found in the reaction of 1 with ethyllithium which affords 5-ethylcycloocta-2,6-dienone (70·2%) in ether, and also in the metal salts (MgBr₂, LiBr, and LiClO₄) induced isomerization giving cycloheptatrienylcarboxyaldehydes and phenylacetaldehyde. The diverse nature of the products in the reactions is accounted for by the formation of homotropylium cation intermediates.     

The 3− state in the doubly closed shell nucleus 64 146 Gd82

Inbeam γ-ray angular distribution measurements establishI ^π = 3^? for the 1579 keV first excited state in¹⁴⁶Gd.     

Translational energy distribution of the excited hydrogen atom produced by controlled electron impact on HCl

The translational energy distribution of an atom can be calculated by differentiating the Doppler line shape of its emission line taken at a high optical resolution. The Balmer-β line of the excited hydrogen atom (n = 4) produced by electron impact on HCl has been measured at a high resolution (0.033Å) and at two angles (55° and 90°) with respect to the electron beam. The translation energy distribution depends on the electron energies and has almost two groups of components: ≈ 5 eV (fast) and ≈ eV (slow). Anisotropy is imporant for the slow component. The excitation function shows the corresponding structures. It is concluded that Rydberg states converging to the ²Π state of HCl⁺ produce the fast component and Rydberg states converging to the repulsive HCl⁺ states which cross the ²Σ⁺ state produce the slow component.