Temperature dependence of pressure broadening and shifts of acetylene at 1550 nm by He, Ne, and Ar

Pressure broadening and shift coefficients for the ν₁+ν₃ band of ¹²C₂H₂ have been measured for He, Ne, and Ar at a temperature of 195 K using high resolution diode laser spectroscopy. The pressure broadening and shifts follow patterns with rotational assignment that are similar to those at room temperature but are generally larger in magnitude. The change in magnitude is qualitatively described by assuming, for each transition, a constant cross section for pressure broadening or shifting. Better agreement may be obtained for pressure broadening coefficients by using empirically determined temperature exponents; better agreement still is obtained from close coupling calculations of the pressure broadening cross sections. PACS 33.70.Jg     

Raman spectroscopic and structural studies of heat-treated graphites for lithium-ion batteries

Standard graphite TIMREX® SLX 50 was oxidised at 500–800 °C under air atmosphere in a muffle and a rotary furnace. Scanning Electron Microscopy (SEM), Raman spectroscopy, and X-Ray Powder Diffraction (XRD) were used to study the changes in surface morphology and crystallinity. The results show a slight increase of the L_a value and a decrease of the rhombohedral fraction with increased heat-treatment temperature (HTT). XRD measurements show no significant change in L_a values within the bulk of graphite samples. Above 700 °C SEM images of graphite reveals holes and cavities, whereas heat-treatment temperatures below 700 °C do not significantly affect graphite materials parameters.     

Forward particle production in π− p andK − p collisions at 58 GeV/c and comparison with quark models

We present single inclusive π^±, π⁰ andK ^± spectra in the forward fragmentation region (x>0.2,p _T <1.5 GeV/c) as well as correlations between two charged particles. The data were recorded in an unseparated negative hadron beam at the CERN SPS using a large acceptance forward spectrometer. Our maasurements are compared in detail with several models which emphasise the role of the beam valence quarks in this production process. The connection to measurements at largep _T is also investigated.     

The 2B1 ← 2A1 system of nitrogen dioxide

The vibrational structure of the ²B₁ ← ²A₁ system of NO₂ has been assigned to a progression in ν′₂. Vibrational analyses for three isotopic species have been made using a hamiltonian which allows explicitly for a large-amplitude bending vibration. The system origin for the normal isotopic species has been assigned an extrapolated value of 14743.5 cm^?1. The bending potential function is expressed as a rapidly converging Taylor series expansion about the linear configuration. There is no evidence that the equilibrium configuration is nonlinear.     

Solvent‐Mediated Control of the Electrochemical Discharge Products of Non‐Aqueous Sodium–Oxygen Electrochemistry

The reduction of dioxygen in the presence of sodium cations can be tuned to give either sodium superoxide or sodium peroxide discharge products at the electrode surface. Control of the mechanistic direction of these processes may enhance the ability to tailor the energy density of sodium–oxygen batteries (NaO₂: 1071 Wh kg^?1 and Na₂O₂: 1505 Wh kg^?1). Through spectroelectrochemical analysis of a range of non‐aqueous solvents, we describe the dependence of these processes on the electrolyte solvent and subsequent interactions formed between Na⁺ and O₂^?. The solvents ability to form and remove [Na⁺‐O₂^?]_ads based on Gutmann donor number influences the final discharge product and mechanism of the cell. Utilizing surface‐enhanced Raman spectroscopy and electrochemical techniques, we demonstrate an analysis of the response of Na‐O₂ cell chemistry with sulfoxide, amide, ether, and nitrile electrolyte solvents.     

Memory of Chirality in Flow Electrochemistry: Fast Optimisation with DoE and Online 2D-HPLC

Amino acid derivatives undergo non-Kolbe electrolysis to afford enantiomerically enriched α-alkoxyamino derivatives through intermediate chiral carbenium ions. The products contain N,O-acetals which are important structural motifs found in bioactive natural products. The reaction is performed in a continuous flow electrochemical reactor coupled to a 2D-HPLC for immediate online analysis. This allowed a fast screening of temperature, electrode material, current, flow-rate and concentration in a DoE approach. The combination with online HPLC demonstrates that also stereoselective reactions can benefit from a hugely accelerated optimisation by combining flow electrochemistry with multidimensional analysis.