Effect of inter-miniband tunneling on current resonances due to the formation of stochastic conduction networks in superlattices

We study the effects of inter-miniband electron tunneling and electric field domains on the current–voltage and conductance–voltage curves of biased semiconductor superlattices under the action of a magnetic field that is tilted relative to the plane of the layers. For this geometry, electrons in the superlattice minibands exhibit a unique type of stochastic semiclassical motion. At certain critical values of the electric field within the superlattice layers, the stochastic trajectories change abruptly from fully localized to completely unbounded, and map out an intricate web-like mesh of conduction channels in phase space. Delocalization of the electron paths produces a series of strong resonant peaks in the electron drift velocity versus electric field curves. We use these drift velocity characteristics to make self-consistent drift-diffusion calculations of the current–voltage and differential conductance–voltage curves of the superlattices, which reveal strong resonant features originating from the sudden delocalization of the stochastic single-electron paths. We show that this delocalization has a pronounced effect on the distribution of space charge and electric field domains within the superlattices. Inter-miniband tunneling greatly reduces the amount of space-charge buildup, thus enhancing the domain structure and both the strength and number of the current resonances.     

Li+ transport in Li0.40MoO3 studied by pulse NMR

Pulsed ⁷Li NMR relaxation time measurements are reported for the intercalate Li_0.40MoO₃ in the temperature range 200K < T < 460K at 20 MHz. Temperature dependences of T₁ and T₂ indicate translation of Li⁺ with E_A = 23 kJ mol^-1. The data lead to an estimate for the Li⁺ self-diffusion coefficient at 300K of D¹_300K ? 4 x 10^-12 cm² sec^-1.     

Collisional transfer of rotational energy in the 2B1 electronic state of nitrogen dioxide

Collisional satellite lines have been observed in fluorescence from nitrogen dioxide excited by the 4545-Å line of the argon laser. The 13_0,13 level of the (0, 8, 0) vibrational state is populated by the laser and undergoes collisionally induced transitions to the 11_0,11, 15_0,15, and 17_0,17 states. These collisionally populated states are identified by their fluorescence to the well-studied (0, 0, 0) and (0, 1, 0) levels of the ground electronic state. These satellite lines are also observed in fluorescence to the (0, 2, 0) and (0, 3, 0) vibrational levels of the ground electronic state. The wavenumbers of those lines, together with those from unrelaxed fluorescence and previously published microwave transitions, allow vibrational and rotational constants for the higher vibrational states to be determined more accurately than was previously possible. Several much weaker forbidden transitions have also been observed, including ΔK_a = 0 through ?6 transitions in the (0, 8, 0)-(0, 0, 1) band.     

Evidence for a spin-5 boson resonance at 2300 MeV

Evidence is given for the existence of a spin-5 boson resonance from the analysis of the reaction π^?p→K⁺K^?n at 62 GeV incident momentum. A simplified amplitude analysis with a Breit-Wigner ansatz leads to a mass 2307 ± 6 MeV and a width of 245 ± 20 MeV. The quantum numbers of the resonance are J^P = 5^?, C = ?1, and very probably I^G = 1⁺.     

Measurement ofD meson production in 200 GeV π−-Be interactions

We have measured the differential and total cross sections ofD meson production in 200 GeV π^?-beryllium interactions, using a sample of 48 fully reconstructed and nearly background-freeD mesons in the decay channelsK ^?π^±,K ^?π^±π^± andK ^?π^?π^±π^±. A single electron trigger has been used to select events containing a pair of charmed particles. A vertex telescope of 6 silison microstrip detectors allowed the reconstruction of tracks of charged secondaries and the reconstruction of primary and decay vertices with high precision. The ratio of branching fractions for \(\mathop {D^0 }\limits^{( - )} \to K^ \mp \pi ^ \pm \) to \(\mathop {D^0 }\limits^{( - )} \to K^ \mp \pi ^ \mp \pi ^ \pm \pi ^ \pm \) , and an upper limit for \(D^0 - \bar D^0 \) mixing are presented.