An apparatus for the production of high isotopic purity deuterium

An apparatus for the electrolytic preparation of high purity D2 is described. D2 with isotopic purity exceeding 99.98% (atomic percentage) was obtained with this apparatus by electrolysing D2O (99.8% isotopic purity) down to about 30% of its original volume

Variable angle photoelectron spectroscopy of the fluoroethylenes

He I photoelectron spectra of fluoroethylene, 1,1‐difluoroethylene, cis‐1,2‐difluoroethylene, trans‐1,2‐difluoroethylene, trifluoroethylene, and perfluoroethylene were obtained over the scattering angle range of 45° to 120° and compared with those of ethylene. Vibrational frequencies of the ionic states were measured and their symmetry modes assigned. The asymmetry parameter β as a function of the ionization potential was measured for each molecule. The value of β for the first ionization potential band of these molecules was found to decrease monotonically with increasing fluorine substitution. This variation was interpreted as being due to resonance mixing of the lone pair F π orbitals with C–C π orbitals. The data obtained were used to assign some of the spectral bands observed

Doublet→quartet and doublet→doublet electronic transitions in NO2 by electron impact

The electron-impact energy-loss spectrum of nitrogen dioxide (NO2) has been measured at impact energies of 25, 50, and 75 eV, and scattering angles varying from 5° to 80°. A previously unreported spin-forbidden doublet→quartet transition was observed at 4.49 eV, in excellent agreement with theoretical calculations. Doublet→doublet transitions were observed at 2.95, 5.81, 7.48, 8.64, 9.69, 10.52, 10.68, 10.94, and 11.20 eV, in agreement with previous experimental and theoretical work. In addition, numerous doublet→doublet transitions to superexcited states were observed

Electron-impact spectroscopy of acetaldehyde

Acetaldehyde has been studied by the technique of low‐energy variable‐angle electron energy‐loss spectroscopy. With this method the low‐lying spin‐forbidden transitions have been located via the behavior of the relative differential cross sections, providing the first identification by this technique of such states in acetaldehyde. High‐lying states were also investigated and some assignments of dipole symmetry‐forbidden/quadrupole symmetry‐allowed excitations were made on the basis of characteristic angular behavior, evident for the asymmetric molecule acetaldehyde just as for the symmetric molecules formaldehyde and acetone. Through a comparison of the acetaldehyde results with those for formaldehyde and acetone the trends in the allowed and forbidden transition energies were examined as a function of methyl substitution and found to be relatively linear

Photoacoustic detection of stimulated emission pumping in p-difluorobenzene

Photoacoustic detection has been used to monitor a stimulated emission pumping process in p‐difluorobenzene. Using the Ã^(1)B_(2u)5^1 state as an intermediate, several vibrational levels of the ground electronic state were populated. The photoacoustic method is an attractive alternative to other detection techniques because of its sensitivity, simplicity, and its ability to differentiate between stimulated emission pumping and excited state absorption. An example of excited state absorption in aniline is given

Automated mass spectrometer/analysis system: A concept

System performs rapid multiple analyses of entire compound classes or individual compounds on small amounts of sample and reagent. Method will allow screening of large populations for metabolic disorders and establishment of effective-but-safe levels of therapeutic drugs in body fluids and tissues

Towards a state-to-state transition state theory

We assume that, having arrived at the transition state, the branching into the different product states is independent of the initial quantum states of the reactants. This assumption plus the familiar transition state approximation (that the reaction rate is the rate of the passage across the barrier) yields an expression for the state-to-state cross section in terms of the state-to-all one, as well as microcanonical rate constants. Models, adiabatic correlations, purely statistical considerations, or collinear computations can provide the required input for the theory. Exact quantal computations on the 3D H + H2 reaction are found to satisfy the assumed factorization quite well. Furthemore, reaction probabilities derived from a line-of-centers model, with a barrier height dependent on the approach angle, account for the probabilities derived from the exact quantal computation

Collinear quasiclassical trajectory study of collision-induced dissociation on a model potential energy surface

Quasiclassical trajectory calculations have been carried out at energies above the threshold for collision-induced dissociation for a model symmetric collinear atom–diatomic molecule system. Exact quantum mechanical calculations have shown that quasiclassical trajectories give a qualitatively correct picture of the dynamics in this system, in so far as reaction and total dissociation probabilities are concerned. Trajectories leading to dissociation are found to lie almost entirely in well-defined reactivity bands, with the exception of a few occurring in a small chattering region in which the outcome of the trajectory is extremely sensitive to its initial conditions. The energy distribution functions of the dissociated atoms are obtained and shown to vary substantially with initial conditions (reagent vibrational and translation energy). The form of these distributions is, to a major extent, determined by the position and width of the reactivity bands. The different dissociation reactivity bands are shown to be associated with different types of trajectories. Part of the vibrational enhancement of dissociation arises from the fact that the simplest possible trajectory leading to dissociation (one which crosses the symmetric stretch line only once prior to the onset of dissociation) is not obtained with ground state reagents