Intrinsic mobility limit for anisotropic electron transport in Alq3

Muon spin relaxation has been used to probe the charge carrier motion in the molecular conductor Alq3 (tris[8-hydroxy-quinoline] aluminum). At 290 K, the magnetic field dependence of the muon spin relaxation corresponds to that expected for highly anisotropic intermolecular electron hopping. Intermolecular mobility in the fast hopping direction has been found to be 0.23+/-0.03 cm2 V-1 s(-1) in the absence of an electric- field gradient, increasing to 0.32+/-0.06 cm2 V-1 s(-1) in an electric field gradient of 1 MV m(-1). These intrinsic mobility values provide an estimate of the upper limit for mobility achievable in bulk material.     

Muon spin relaxation in solid3He

Muon spin relaxation in solid³He depends non-monotonously on the temperature. It is shown that this is entirely due to the magnetic dipole-dipole interactions. The observed line narrowing cannot be explained by the mechanism of positive charge hopping described by an Arrhenius-like law. The relaxation rate at low temperatures was found to increase under the influence of an external electric field.     

Search for dark matter production in association with the Z' boson at the LHC in pp collisions at s~(1/2)= 8 TeV using Monte Carlo simulations

This analysis evaluates the possibility of the search for Dark Matter(DM) particles using events with a Z' heavy gauge boson and a large missing transverse momentum at the Large Hadron Collider(LHC).We consider the muonic decay of Z'.The analyzed Monte Carlo samples were the Open simulated files produced by the Compact Muon Solenoid(CMS) collaboration for proton-proton collisions,corresponding to an integrated luminosity of the LHC run-I with 19.7 fb~(-1) at s~(1/2)=8 TeV.Two scenarios,namely a simplified benchmark scenario,called Dark Higgs,and the effective field theory(EFT) formalism,were used for interpretations.Limits were set on Z'. dark matter masses,and the cutoff scale of the EFT.     

Electromagnetic secondaries and punch-through effects in the CMS ME1/1

The aim of this work is to estimate the shower leakage from the CMS Endcap Hadron calorimeter (HE) due to electromagnetic secondaries and punch-through in the region of the ME1/1 Forward Muon Station. Two configurations are considered: with and without the CMS Endcap Electromagnetic calorimeter (EE). The experimental data have been taken during the combined beam test of CMS subdetectors (HE, ME, RPC, DT) at the CERN H2 beam facility in 2004. Serial CSC chambers (ready for installation in CMS) fully equipped with readout electronics have been exposed. Simulation of a beam test setup has been performed using the GEANT4-based simulation software package OSCAR. The text was submitted by the authors in English.     

Commissioning of the New sMDT Monitored Drift Tube Detectors for the Phase-1 Upgrade of the ATLAS Muon Spectrometer

Physics of Atomic Nuclei - The Muon Drift Tube (MDT) chambers provide very precise and reliable muon tracking and momentum measurement in the ATLAS muon spectrometer. Already in Run 2 of the LHC...     

Field dependence of the muon spin relaxation rate in MnSi

Muon spin rotation/relaxation measurements have been performed in the itinerant helical magnet MnSi at ambient pressure and at 8.3 kbar. We have found the following: (a) the spin-lattice relaxation rate 1/T(1) shows divergence as T1T proportional, variant (T-T(c))(beta) with the power beta larger than 1 near T(c); (b) 1/T(1) is strongly reduced in an applied external field B(L) and the divergent behavior near T(c) is completely suppressed at B(L)> or =4000 G. We discuss that (a) is consistent with the self-consistent renormalization theory and reflects a departure from "mean-field" behavior, while (b) indicates selective suppression of spin fluctuations of the q=0 component by B(L).     

Rydberg原子nS1/2→(n+1)S1/2双光子激发EIT-AT光谱

主要研究了热原子蒸气池中铯Rydberg原子nS_1/2→(n+1)S_1/2微波耦合的双光子光谱.铯原子基态(6S_1/2)、第一激发态(6P_3/2)、Rydberg态(69S_1/2)形成阶梯型三能级系统,弱探测光作用于基态到激发态6S_1/2→6P_3/2的跃迁,强耦合光则作用于6P_3/2→69S_1/2的Rydberg跃迁形成电磁感应透明(EIT)效应,实现对Rydberg原子的光学探测.频率fMW=11.735 GHz的微波场耦合69S_1/2→70S_1/2的Rydberg跃迁,形成微波双光子光谱.利用EIT-AT分裂光谱研究微波电场强度对双光子光谱的影响.研究表明:在强微波场作用时,EIT-AT分裂与微波场功率成正比,而弱微波场时的EIT-AT分裂与微波场功率成非线性依赖关系,理论计算与实验测量结果相一致.本文的研究对微波电场的精密测量具有一定的指导意义.     

The effects of large oscillating fields on spin precession in magnetic resonance

Magnetic resonance of a spin system which is acted upon by a large near-resonance oscillating magnetic field transverse to a static field has been studied experimentally and theoretically for many years. The technique of DEMUR (Double Electron Muon Resonance) has many advantages for such studies. This paper will describe the results of an experiment to study the precession of the muonium triplet near magnetic resonance using DEMUR.     

Electrostatic ion-cyclotron wave experiments in the WVU Qmachine

The influence of transverse, localized, DC electric fields (TLEs) on the current-driven electrostatic ion-cyclotron (CDEIC) instability is being investigated in a Q machine. A small (diameter ~10 ion gyroradii) segmented disk electrode is being used to excite the mode in a narrow electron-current channel along which exists a radial electric field between regions that magnetically map to the different circular segments (separated by a radial gap of ~3 ion gyroradii). Experiments aimed at demonstrating a TLE dependence in the threshold current for mode excitation are described. A comparison of observed and predicted mode frequencies over a range of magnetic field strengths is presented for the benchmark case of no applied transverse electric field. When the electric field is present, ion-cyclotron fluctuations are observed for cases in which the current is below the CDEIC instability threshold     

Influence of magnetic field on scintillators brightening in hadron calorimeters of endcap parts of Compact Muon Solenoid plant of Large Hadron Collider

The influence of magnetic field on brightening of scintillators of endcap hadron calorimeters of the Compact Muon Solenoid (CMS) plant of the Large Hadron Collider (LHC) has been investigated. Experimental studies were performed with cosmic ray muons in real configuration of the CMS plant with magnetic field (B = 3.8 T) turned on and off. It was shown that the magnetic field increases the brightening of scintillators by 8.4%.     

Evidence for static magnetism in the vortex cores of ortho-II YBa2Cu3O6.50

Evidence for static alternating magnetic fields in the vortex cores of underdoped YBa2Cu3O6+x is reported. Muon spin rotation measurements of the internal magnetic field distribution of the vortex state of YBa2Cu3O6.50 in applied fields of H = 1 T and H = 4 T reveal a feature in the high-field tail of the field distribution which is not present in optimally doped YBa2Cu3O6.95 and which fits well to a model with static magnetic fields in the vortex cores. The magnitude of the fields is estimated to be 18(2) G and decreases above T = 10 K. We discuss possible origins of the additional vortex core magnetism within the context of existing theories.     

The Electric Dipole Moment of the B(1)Pi State of ZrO

A laser ablation source combined with a time-of-flight mass spectrometer has been constructed. The static electric field in the mass spectrometer gives rise to a first-order Stark effect splitting from which the permanent electric dipole moment of the B(1)Pi state (v = 0) of (90)ZrO is determined and found to be 3.43 +/- 0.07 D. The X(1)Sigma and B(1)Pi states are further investigated and comparisons with the results from ab initio calculations are made. Copyright 2000 Academic Press.     

Kinetic normal ordering and the 1 + 1 dimensional U(1) anomaly

We consider 1 + 1 dimensional, massless fermions coupled to an external electric field. We show that, contrary to common belief, the computation of the chiral anomaly involves no divergences and no ambiguities. The computation is done in hamiltonian formalism and is based on two steps: (I) the computation of the Schwinger term in the equal time commutator of currents, (II) the physically correct normal ordering with respect to kinetic energy.     

A microscopic semiclassical confining field equation forU(1) lattice gauge theory in 2+1 dimensions

We present a semiclassical nonlinear field equation for the confining field in 2+1-dimensionalU(1) lattice gauge theory (compact QED). The equation is derived directly from the underlying microscopic quantum Hamiltonian by means of truncation. Its nonlinearities express the dynamic creation of magnetic monopole currents leading to the confinement of the electric field between two static electric charges. We solve the equation numerically and show that it can be interpreted as a London relation in a dual superconductor.     

Low temperature limit of the vortex core radius and the kramer-pesch effect in NbSe2

Muon spin rotation ( &mgr;SR) has been used to measure the magnetic field distribution in the vortex state of the type-II superconductor NbSe2 ( T(c) = 7.0 K) below T = 2 K. The distribution is consistent with a highly ordered hexagonal vortex lattice with a well resolved high-field cutoff associated with the finite size of the vortex cores. The temperature dependence of the core radius is much weaker than the temperature dependence predicted from the Bogoliubov-de Gennes theory. Furthermore, the vortex radius measured by &mgr;SR near the low temperature quantum limit is about an order of magnitude larger than predicted.     

Coexistence of magnetic fluctuations and superconductivity in the pnictide high temperature superconductor SmFeAsO1-xFx measured by muon spin rotation

Muon spin rotation experiments were performed on the pnictide high temperature superconductor SmFeAsO1-xFx with x=0.18 and 0.3. We observed an unusual enhancement of slow spin fluctuations in the vicinity of the superconducting transition which suggests that the spin fluctuations contribute to the formation of an unconventional superconducting state. An estimate of the in-plane penetration depth lambda ab(0)=190(5) nm was obtained, which confirms that the pnictide superconductors obey an Uemura-style relationship between Tc and lambda ab(0);(-2).     

Crystal electric field next to a hydrogen-like interstitial— µ+ in PrNi5

Muon spin rotation measurements of the temperature dependence and the anisotropy of the μ⁺ Knight shift in single crystals of the crystal electric field singlet ground state system PrNi₅ reveal pronounced deviations from a linear scaling of the Knight shift with the bulk magnetic susceptibility atT≤50 K. They are explained by a μ⁺ induced modification of the atomic susceptibility of neighboring Pr³⁺ ions. From the Knight shift anisotropy atT> 50 K it is determined that the implanted μ⁺ occupy a single intersitial site, namely the 6i site (0.5, 0, 0.21±0.02). Using this site information, good model fits to the measured data are obtained assuming a μ⁺ induced perturbation of the crystal electric field at the Pr³⁺ ions next to the μ⁺. Apparently, the presence of the μ⁺ leads to a lowering of the local symmetry, causing a lifting of the degeneracy and a pronounced rearrangement of the low lying crystal electric field levels for these ions.     

不同电场下碳纳米管场致发射电流密度研究

本文运用密度泛函理论和金属电子论, 深入研究了碳纳米管场致发射电流的变化规律. 结果显示其发射电流密度取决于体系的态密度、赝能隙、管长和局域电场, 在不同范围电场下的变化规律不同. 在较低电场下, 发射电流密度随电场增强而近似线性增大(对应的宏观电场须小于18 V· μm^-1); 但在较高电场下, 发射电流密度随外电场增加呈现非周期性振荡增长趋势, 碳纳米管表现为电离发射. 本文进一步研究了金属性碳纳米管电导率在不同电场下的变化规律.     

Performance study of new style mosaic MRPC

The Compact Muon Solenoid (CMS) at LHC intends to use a high rate trapezoid MRPC for the muon system upgrade, but the size of the MRPC is limited by the dimensions of low resistivity glass. We have designed a prototype of a large MRPC in which the electrodes are developed by gluing two pieces of glass plates. Simulation of the weighting field and cosmic ray test shows that the efficiency of the glued MRPC is higher than 96% and the time resolution is better than 71 ps.     

Excitation of a hydrogen atom by bichromatic radiation with the frequency ratio 1:2 in the presence of electric field

In the framework of perturbation theory, a probability of excitation of a hydrogen atom from the ground to the first excited state under bichromatic laser radiation with the frequency ratio 1:2 in the presence of electric field is calculated, taking into account quantum interference of two process channels. In the case under study, a coherent superposition of the 2s-and 2p-states, necessary for quantum interference to occur, is formed under the action of the external electric field. The excitation probability is analyzed depending on the relative phase of monochromatic radiation components (the coherent phase control) for two extreme cases: for a strong electric field, where the Stark splitting of an upper level essentially exceeds the spin-orbit one, and for the contrary limit of a weak field. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 20–28, August, 2006.