Dilepton and trilepton production by antineutrinos and neutrinos in neon

A sample of over 25,000 fully measured neutrino and antineutrino charged current interactions in BEBC includes 192 dilepton candidates. The prompt signal after subtraction of background is 41 ±7µ⁺ e ^-, 35±7µ⁺µ^- events from \(\bar v\) interactions, and 32±7µ^-µ⁺ events from ν interactions. There are 2 trileptons, µ^-µ^- e ⁺ and µ^-µ^-µ⁺. Results are compared with other experimental data and with the standard model. Limits to prompt like sign µ⁺ e ⁺, µ⁺µ⁺ and µ^-µ^- signals are given and compared with other experiments and with theoretical calculations.     

Bestimmung der Harns?ure und der Xanthinbasen

Ohne Zusammenfassung     

Electrospray ionization mass spectrometry of stable nitroxide free radicals and two isoindoline nitroxide dimers

Electrospray ionization (ESI) mass spectra were recorded for a range of substituted isoindoline nitroxides, two isoindoline nitroxide dimers and two piperidinyl nitroxides. In all cases the dominant molecular species arise from oxidation rather than protonation, an unusual process in ESI. Fragment ion spectroscopy was used to establish fragmentation mechanisms for the nitroxides under ESI conditions.     

Electrospray mass spectrometry of stable iminyl nitroxide and nitronyl nitroxide free radicals

Electrospray ionization (ESI) mass spectra have been recorded for a range of substituted nitronyl nitroxide and iminyl nitroxide monoradicals and biradicals. Secondary species formed in the ESI source were observed as the dominant ions in both the iminyl nitroxide and nitronyl nitroxide spectra. Daughter ion spectrometry was used to establish fragmentation mechanisms for the nitronyl nitroxide and iminyl nitroxide moieties as well as the secondary species under ESI conditions.     

CO bond cleavage on supported nano-gold during low temperature oxidation

The oxidation of CO by Au/Fe(2)O(3) and Au/ZnO catalysts is compared in the very early stages of the reaction using a temporal analysis of products (TAP) reactor. For Au/Fe(2)O(3) pre-dosing the catalyst with (18)O labelled water gives an unexpected evolution order for the labelled CO(2) product with the C(18)O(2) emerging first, whereas no temporal differentiation is found for Au/ZnO. High pressure XPS experiments are then used to show that CO bond cleavage does occur for model catalysts consisting of Au particles deposited on iron oxide films but not when deposited on ZnO films. DFT calculations, show that this observation requires carbon monoxide to dissociate in such a way that cleavage of the CO bond occurs along with dynamically co-adsorbed oxygen so that the overall process of Au oxidation and CO dissociation is energetically favourable. Our results show that for Au/Fe(2)O(3) there is a pathway for CO oxidation that involves atomic C and O surface species which operates along side the bicarbonate mechanism that is widely discussed in the literature. However, this minor pathway is absent for Au/ZnO.     

Magnetochemical Properties and Reactions of Vanadium(III) Thiolate Complexes: Preparation of (NEt(4))(3)[V(3)Cl(6)(edt)(3)] and Mixed-Valence (NEt(4))[V(2)(edt)(4)] (edt = Ethane-1,2-dithiolate)

Reactions of the previously reported dinuclear vanadium(III) thiolate anion [V(2)(edt)(4)](2)(-) (edtH(2) = ethane-1,2-dithiol) are described. Treatment of (NEt(4))(2)[V(2)(edt)(4)] (1) in MeCN with equimolar (C(12)H(8)S(2))BF(4) (C(12)H(8)S(2)(+) = the thianthrenium radical cation) results in a one-electron oxidation and isolation of the V(III),V(IV) complex (NEt(4))[V(2)(edt)(4)] (2). The same product can also be obtained by controlled-potential electrolysis of 1 at -0.20 V vs Ag/AgCl. Treatment of 1 in CH(2)Cl(2) with py gives no reaction, but addition of Me(3)SiCl leads to formation of the known V(2)OCl(4)(py)(6) (3). The latter is also formed by the reduction of a 1:1 mixture of VOCl(3) and VCl(3)(THF)(3) in CH(2)Cl(2)/py and by the reaction in CH(2)Cl(2) of VCl(3)(THF)(3) and py with edt(2)(-). Treatment of 1 in MeCN with bpy (2,2'-bipyridine) gives no reaction, but addition of Me(3)SiCl results in formation and isolation of [V(2)OCl(2)(bpy)(4)]Cl(2) (4) identified by spectroscopic comparison with literature data. The reaction of 1 in MeCN with equimolar VCl(3)(THF)(3) and NEt(4)Cl gives (NEt(4))(3)[V(3)Cl(6)(edt)(3)] (5). A more convenient procedure to 5 is the reaction in MeCN of VCl(3)(THF)(3), Na(2)edt, and NEt(4)Cl in a 1:1:1 molar ratio. Complex 5.MeCN crystallizes in triclinic space group P&onemacr; with (at -154 degrees C) a = 14.918(3) ?, b = 17.142(5) ?, c = 11.276(3) ?, alpha = 106.78(1) degrees, beta = 95.03(1) degrees, gamma = 106.18(1) degrees, and Z = 2. The anion contains a near-linear V(3) unit with a face-sharing trioctahedral structure: the three edt(2)(-) groups provide the six bridging S atoms; two edt(2)(-) groups are in a &mgr;-eta(2):eta(2) mode (as in 1), but the third is in a &mgr;(3)-eta(1):eta(2):eta(1) mode. The V.V separations (>3.1 ?) preclude V-V bonding. Variable-temperature solid-state magnetic susceptibility studies have been performed on complexes 1, 2, and 5 in a 1.0 kG field and 5.00-300 K temperature range. For 1, the effective magnetic moment (&mgr;(eff)) gradually decreases from 1.09 &mgr;(B) at 300 K to 0.26 &mgr;(B) at 5.00 K. The data were fit to the Bleaney-Bowers equation, and the fitting parameters were J = -419(11) cm(-)(1) and g = 2.05. The singlet-triplet gap is thus 838 cm(-)(1). For 2, &mgr;(eff) is essentially temperature-independent, slowly decreasing from 1.90 &mgr;(B) at 300 K to 1.86 &mgr;(B) at 55 K and then to 1.63 &mgr;(B) at 5.00 K. The complex thus is S = (1)/(2) with no thermally accessible S = (3)/(2) state. The combined data on 1 and 2, together with the results of EHT calculations, show that 1 and 2 contain a V-V single bond tying up two of the d electrons and that the remaining two d electrons in 1 are antiferromagnetically coupled to give an S = 0 ground state and S = 1 excited state; for 2, the one remaining d electron gives an S = (1)/(2) state. For 5, &mgr;(eff) increases from 5.17 &mgr;(B) at 320 K to a maximum of 6.14 &mgr;(B) at 30.0 K and then decreases slightly to 6.08 &mgr;(B) at 5.00 K. The data were fit to the appropriate theoretical expression to give J = +42.5(6) cm(-)(1), J' = -1.8(5) cm(-)(1), and g = 1.77, where J and J' gauge the interactions between adjacent and terminal V(III) atoms, respectively. The complex has an S = 3 ground state and represents a very rare example of ferromagnetic coupling between V(III) centers.     

Atmospheric channel characteristics for quantum communication with continuous polarization variables

We investigate the properties of an atmospheric channel for free space quantum communication with continuous polarization variables. In our prepare-and-measure setup, coherent polarization states are transmitted through an atmospheric quantum channel of 100 m length on the flat roof of our institute’s building. The signal states are measured by homodyne detection with the help of a local oscillator (LO) which propagates in the same spatial mode as the signal, orthogonally polarized to it. Thus the interference of signal and LO is excellent and atmospheric fluctuations are auto-compensated. The LO also acts as a spatial and spectral filter, which allows for unrestrained daylight operation. Important characteristics for our system are atmospheric channel influences that could cause polarization, intensity and position excess noise. Therefore we study these influences in detail. Our results indicate that the channel is suitable for our quantum communication system in most weather conditions.     

Study of structural and electronic transport properties of Ce-doped LaMnO3

The structural and electronic transport properties of La_1−x Ce _x MnO₃ (x=0.0–1.0) have been studied. All the samples exhibit orthorhombic crystal symmetry and the unit cell volume decreases with Ce doping. They also make a metal-insulator transition (MIT) and transition temperature increases with increase in Ce concentration up to 50% doping. The system La_0.5Ce_0.5MnO₃ also exhibits MIT instead of charge-ordered state as observed in the hole doped systems of the same composition.