Rotational analysis of the 8000–9000 Å bands of nitrogen dioxide

The rotational structure of bands of NO₂ vapor in the region 8300–9000 Å has been partially analyzed and the absorption assigned to the (000)-(000) and (000)-(010) vibronic bands of the $\text{A}\text{?}{}^2\text{B}{}_2\text{←}\text{X}\text{?}{}^2\text{A}{}_1$ electronic transition. Irregular weak perturbations in the N-structure of the upper-state manifold are accompanied by larger resonance-type crossings in the K-structure. The larger perturbation is attributed to vibronic coupling between the à state and excited vibrational levels of the ground state, characterized by a low density of ground state levels and a large vibronic coupling matrix element between the à and X? states. The reconstituted, deperturbed bands have blue-degraded N-structure and strongly red-degraded K-structure, indicating that the bond angle decreases sharply in the excited state. The physical structure of the ²B₂ state is uncertain but some suggestions are made. The electronic energy of the ²B₂ state is T₀ = 11 962.9 cm^?1.     

Reactions in the rechargeable lithium-O2 battery with alkyl carbonate electrolytes

The nonaqueous rechargeable lithium-O(2) battery containing an alkyl carbonate electrolyte discharges by formation of C(3)H(6)(OCO(2)Li)(2), Li(2)CO(3), HCO(2)Li, CH(3)CO(2)Li, CO(2), and H(2)O at the cathode, due to electrolyte decomposition. Charging involves oxidation of C(3)H(6)(OCO(2)Li)(2), Li(2)CO(3), HCO(2)Li, CH(3)CO(2)Li accompanied by CO(2) and H(2)O evolution. Mechanisms are proposed for the reactions on discharge and charge. The different pathways for discharge and charge are consistent with the widely observed voltage gap in Li-O(2) cells. Oxidation of C(3)H(6)(OCO(2)Li)(2) involves terminal carbonate groups leaving behind the OC(3)H(6)O moiety that reacts to form a thick gel on the Li anode. Li(2)CO(3), HCO(2)Li, CH(3)CO(2)Li, and C(3)H(6)(OCO(2)Li)(2) accumulate in the cathode on cycling correlating with capacity fading and cell failure. The latter is compounded by continuous consumption of the electrolyte on each discharge.     

Investigation of H+ motion in the 21-hydrates of 12-tungstophosphoric and 12-molybdophosphoric acids by ac conductivity and pulsed 1H NMR measurements

AC conductivity and ¹H NMR relaxation time measurements are reported for the heteropolyacids H₃PM₁₂O₄₀. 21H₂O (M = W, Mo) over a range of tempereatures.Ambient temperature proton conductivites are ? 1 S m^-1, with conductivity activation energies E ? 40 kJ mol^-1.The NMR results are interpreted in terms of a range of motional processes leading to distributions of translational correlation times. The behaviour is compared to motions in zeolites and of water sorbed by charcoal.     

A measurement of the beam asymmetry parameter Σ for neutral pion photoproduction in the energy range 1.2–2.8 GeV

An experiment has been completed at the Daresbury synchrotron to measure the asymmetry in the photoproduction cross section of neutral pions on hydrogen, for photons polarised normal to and in the production plane. The source of polarised photons was coherent bremsstrahlung of electrons traversing the lattice structure of diamond and the polarisation P of the γ beam was calculated from the measured intensity of the coherent spike. The asymmetry parameter Σ, defined as Σ = (σ⊥ ? σ|)/(σ⊥ + σ|) where σ⊥(σ|) are the cross sections for photons polarised perpendicular (parallel) to the production plane, has been measured over a range of photon energies from 1.2 to 2.8 GeV and over a range of ?t (the square of the four-momentum transfer) from 0.13 (GeV/c)² to 1.4 (GeV/c)². A marked energy variation in the value of Σ is found over the energy region 1.6–1.8 GeV.     

Nondestructive evaluation of explosively welded clad rods by resonance acoustic spectroscopy

A resonance acoustic spectroscopy technique is assessed for nondestructive evaluation of explosively welded clad rods. Each rod is modeled as a two-layered cylinder with a spring-mass system to represent a thin interfacial layer containing the weld. A range of interfacial profiles is generated in a set of experimental samples by varying the speed of the explosion that drives the copper cladding into the aluminum core. Excellent agreement is achieved between measured and calculated values of the resonant frequencies of the system, through appropriate adjustment of the interfacial mass and spring constants used in the wave scattering calculations. Destructive analysis of the interface in the experimental specimens confirms that key features of the interfacial profile may be inferred from resonance acoustic spectroscopy analysis applied to ultrasonic measurements.     

The polarised beam asymmetry in photoproduction of eta mesons from protons at 2.5 GeV and 3.0 GeV

Measurements of the polarised beam asymmetry parameter Σ for eta photoproduction from protons, have been carried out at incident energies of 2.5 GeV and 3.0 GeV, and for various t-values between ?0.2 (GeV/c)² and ?1.2 (GeV/c)². The values of Σ are close to +1 for values of |t| less than 0.7 (GeV/c)², showing that there can be little contribution from unnatural parity exchange in any Regge exchange model of the process, in disagreement with present theories. Differential cross sections for the process werre also measured, and are consistent with those from other experiments.     

Upper limits for charm production in 150 GeV p-Be interactions

A search has been made for the hadronic production of charmed baryons and mesons with a large aperture forward magnetic spectrometer using 150 GeV protons originating from the CERN-SPS. A prompt electron trigger was used as a signature for charm. Upper limits at 90% confidence level have been obtained for the production of $\text{Λ}{}_{\mathrm{<mtext>c</mtext>}}{}^{\mathrm{+}}\text{D}{}^0\text{,}\text{D}{}^0\text{D}{}^{\mathrm{+}}\text{and D}{}^{\mathrm{?}}\text{: σ(Λ}{}_{\mathrm{<mtext>c</mtext>}}\text{) ? 8 μ}\text{b}\text{, σ(}\text{D}{}^0\text{) ? 64 μ}\text{b}\text{, σ(}\text{D}{}^0\text{) < 37 μ}\text{b}\text{, σ(}\text{D}{}^{\mathrm{+}}\text{) ? 51 μ}\text{b and}\text{σ(}\text{D}{}^{\mathrm{?}}\text{) ? 49 μ}\text{b}$ per nucleon, assuming linear A dependence. Systematic errors due to uncertainties in branching ratios and to model dependence of the acceptance calculation are discussed.     

High statistics inclusive ϕ meson production at SPS energies

Inclusive ? meson production has been measured for 100 GeV/c and 200 GeV/c incident π^?, \(\bar p\) andK ^?, and for 120 GeV/c and 200 GeV/c incident π⁺,p andK ⁺, using a Be target. A total of 630,000 ? mesons has been recorded in the kinematic range 0<x _F <0.4. Presented are the differential cross sectionsdσ/dx _F anddσ/dp _T ². The longitudinal momentum distributions show that the strange valence quarks of the incidentK mesons play an important role in ? meson production, even at smallx _F . The decay angular distribution of the ? meson is evaluated in the Gottfried-Jackson frame and is expressed in the elements of the density matrix. There is a small but significant cos² θ _GJ dependence for smallp _T , which decreases for increasingp _T .