Preferential energy transfer from N2(A) to specific energy levels of Cu atoms

Emission spectra resulting from reaction of “clean” N₂(A³ Σ_u⁺) with copper atoms were studied using a flowing afterglow apparatus. The population distribution of the Cu states was calculated from the spectrum; it indicates that Cu atoms are excited by nearly resonant energy transfer processes. N₂(A,v') + Cu(²S_{$\text{1}\text{2}$}) → N₂(X, v) + Cu^* , and that the transfer is most efficient for N₂(A,v') → N₂(X,v) transitions with large Franck-Condon factors. The preferential energy transfer results in population inversion between some of the Cu states.     

Opening of 3-membered rings to 4π-electron systems : State correlation diagrams including excited states

For the cyclopropyl allyl anion conversion 1 and analog reactions of isoelectronics 2–4 state correlation diagrams are constructed assuming a two step process (ring opening yielding a biradical and a following rotation resulting in the 4π system). The conclusions are supported by MINDO/2 calculations of reaction paths and potential curves. The photochemical reaction possibilities are discussed.     

The retention behavior of radionuclides on copper(ii)sulfide

The adsorption properties of copper(II) sulfide in various acid solutions for different radiotracers are described. Column and batch equilibration methods are discussed. Copper(II) is selectively adsorbed on CuS; the decontamination factor exceeds 10⁶ for column operations in 6 M hydrochloric acid solution. Among the 30 ions tested in 6 M hydrochloric acid, only copper and gold are adsorbed quantitatively; mercury, silver, bromine, technetium and molybdenum are adsorbed partially. The retention capacity for copper(II) is around 20 mg Cu/g CuS. The adsorption processes on CuS as functions of acid concentrations (HCl, HClO₄ and H₂SO₄) are described. The method seems applicable in activation analysis for trace elements in copper matrices.     

On m-changes in atom-rigid-rotor collissions: influence of an initial rotation

Reorientation of the angular momentum of a diatomic molecule in collisions with atoms is investigated using classical mechanics. A factorisation formula for cross sections for rotational excitation is given. The factorisation allows the calculation of the state-specific cross section d σ (j′ m′ ← jm)/dΩ once the m-averaged cross sections d σ (j″← 0 )/dΩ for all possible j″ are known. The approach is applied to the Na₂-He system.     

Crystal structures and phase transition of Rb2TeBr6 (300-12.5 K)

Using 298 and 160(3) K diffractometer intensity data the structure of Rb₂TeBr₆ has been determined by single crystal X-ray technique and refined to a final R_w of 0.041 and 0.037, respectively (K₂PtCl₆ type structure, space group Fm3m, Z = 4 with a₂₉₈ = 10.773(4) Å and a₁₆₀ = 10.713(6) Å). The powder diffraction pattern from 300 to 12.5 K was recorded by a low-temperature Guinier diffractometer and camera. Below 45(5) K a second-order phase transition leads to a tetragonally distorted structure corresponding to a softening of the T_1g(Γ) rotary phonon. The powder pattern measured with the diffractometer at 12.5 K was used for structural refinement (R = 0.092). This low-temperature phase shows a ferrorotative displacement of the TeBr₆-octahedra with a tilt angle of 4.7(1) deg. (space group $\text{I4}\text{m}\text{, Z = 2, a = 7.4726(3)}$ Å and c = 10.7008(5) Å). The structural results indicate that there is no stereochemical activity of the lone pair electrons at Te(IV) even at very low temperatures. Phase transitions of Rb₂TeBr₆ and Rb₂TeI₆ (A_2g(X)-condensation) are compared. The results of a lattice dynamic calculation shows that only the T_1g(Γ) condensation can be explained with a rigid ion model.     

Methane in aqueous solution at 300 K

A Monte Carlo simulation for a methane molecule within a cluster of 202 water molecules is presented and compared with previous studies by Scheraga and Beveridge. Whereas the structural information obtained agrees with previous findings, the energy points to the need for a very large number of Monte Carlo steps and for a different algorithm to compute the partial molar internal energy.     

Fluorescence lifetimes in BO2 (A2Πu)

Fluorescence lifetimes and fluorescence quenching rates are reported for several vibronic levels in the A²Π_u electronic manifold of BO₂. The relationship of these results to earlier Hanle-effect measurements is discussed.     

The association in mixtures of dimethylsulphoxide and water as studied by Raman spectroscopy

In mixtures of dimethylsulphoxide (DMSO) and water, formation of a complex (DMSO) · (H₂O)₂ is indicated by wavenumber shifts and linewidth variations of the v SO Raman band. Higher temperatures interfere with this complex formation.     

Some investigations on new polyphosphates by the anion-exchange method

The structure of the pentamer (a new P-P bonded phosphate) produced by the hydrolysis of dodecaoxohexaphosphoric(III) acid (ring hexamer) has been examined by an anion-exchange distribution method after complex formation with copper(II) and found to be HPO(OH)PO(OH)PO(OH)PO(OH)PO(OH)H. The hexamer and pentamer salts of these P-P bonded linear phosphorus anions have been prepared. The yield of each species was about 1 mole% of the parent material.     

Gas phase electron diffraction study of tetravinyltin Sn(CHCH2)4

The tetravinyltin molecule has been studied by gas phase electron diffraction. The r_a structure analysis is based on the assumptions that a single conformer occurs in Sn(CHCH₂)₄ and that tin has a tetrahedral bond configuration. The preferred model (S₄ symmetry) predicts all four vinyl groups to be intermediate between staggered and eclipsed conformations. The structure refinement gives the following parameters (bond lengths, r_a, in nm, valence angles in degrees):

, SnCC = 121.9(0.6), CC = 0.1349(8), SnCH = 116.8(4.5),<C—H?_av. = 0.1098(14). The uncertainties given in parentheses represent three times the standard deviation values.The observed shortening of the

bond in Sn(CHCH₂)₄ from

in SnMe₄ (by 0.0027 nm) is equal to the shortening that occurs on going from

in ethane to

in propylene. With the corresponding Si and Ge derivatives, this effect is less pronounced.     

The anisotropic van der waals potential for He-N2

We have calculated the spherical v₀ and anisotropic radial components v₂ and v₄ in the usual Legendre expansion for the rigid rotor He-N₂ potential using the method of Tang and Toennies Potential curves covering the range of internuclear distances from 2.5 to 8.0 Å, which includes the minimum region, arc presented and compared with a recent experimental potential derived from differential total cross sections.     

Conformations and electronic properties of alkyl peroxides,alkylperoxy radicals and alkoxy radicals

The equilibrium geometric parameters have been determined for peroxides (H₂O₂, CH₂O₂H, and CH₃O₂CH₃), alkylperoxy radicals (HO₂, CH₃O₂), and C₂H₅O₂), and alkoxy radicals (HO, CH₃O, and C₂H₅O) by means of the semiempirical MINDO/2' method. The predicted bond lengths were found to be more reasonable than those estimated by the CNDO/2 and INDO methods, but the bond angles were predicted too large because of the insufficient parametrizations for such heteroatoms as oxygen. The electronic properties of the above species are also discussed in connection with their physicochemical constants.     

The molecular structure of cyclic methylsiloxanes

A series of methylcyclosiloxanes from the trimer to the hexamer has been investigated by gas phase electron diffraction. The Si-O bond distance varies between 1.635 and 1.620 Å, the SiOSi angle has values from 132° to 149° within the series. The trimer is substantially planar, the best agreement for the tetramer was obtained with a model of S₄. symmetry. As a consequence of large amplitude vibrations, the larger rings do not possess a well-defined conformation. The results are discussed in relation to previous spectroscopic investigations.     

Laser-induced photodissociation of He+2

The momentum distributions of He⁺ fragments from photodissociation of He⁺₂ ions have been recorded in a crossed-beams experiment. The discrete values of the kinetic energy releases can be predicted from the vibrational spacings in the ground state of the primary ions.