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The electron g factor in an ensemble of InAs/InP quantum dots with emission wavelengths around 1.4 μm is measured using time-resolved pump-probe Faraday rotation spectroscopy in different magnetic field orientations. Thereby, we can extend recent single dot photoluminescence measurements significantly towards lower optical transition energies through 0.86 eV. This allows us to obtain detailed insight into the dispersion of the recently discovered g factor anisotropy in these infrared emitting quantum dots. We find with decreasing transition energy over a range of 50 meV a strong enhancement of the g factor difference between magnetic field normal and along the dot growth axis, namely, from 1 to 1.7. We argue that the g factor cannot be solely determined by the confinement energy, but the dot asymmetry underlying this anisotropy therefore has to increase with increasing dot size. [ABSTRACT FROM AUTHOR]

A series of bound exciton transitions of a bulk ZnO sample has been studied by high resolution magnetophotoluminescence spectra. Ten sharp intense bound exciton emissions are classified into three groups according to their dependences on magnetic field, angle, and circular polarization of the emission lines. The charge states of the defect centers and exciton types are identified. The effective g factors of the electrons and holes are determined. [ABSTRACT FROM AUTHOR]

The Zeeman effect in the excited A 2Π3/2 state of CaF is measured and analyzed over a wide range of magnetic fields. It is found that the splitting of the Zeeman levels is largely determined by the coupling between different rotational states and there are no low-field seeking states in the J=3/2 manifold of Zeeman levels at high magnetic fields. A model of the Zeeman spectrum based on the ligand-field theory of CaF is shown to be accurate in the interval of magnetic fields 0–5 Tesla. This demonstrates that the magnetic moment of the CaF(A 2Π3/2) molecule is effectively determined by the spin angular momentum of a single electron and the orbital motion of the valence electron around the Ca2+ core. An analysis of the Zeeman spectrum as a function of the molecular rotational constant indicates that 2Π3/2 molecules should have significant rotational constants (at least as large as twice the rotational constant of CaF) to be amenable to magnetic trapping in high fields.© 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The Zeeman effect in the excited A 2Π3/2 state of CaF is measured and analyzed over a wide range of magnetic fields. It is found that the splitting of the Zeeman levels is largely determined by the coupling between different rotational states and there are no low-field seeking states in the J=3/2 manifold of Zeeman levels at high magnetic fields. A model of the Zeeman spectrum based on the ligand-field theory of CaF is shown to be accurate in the interval of magnetic fields 0–5 Tesla. This demonstrates that the magnetic moment of the CaF(A 2Π3/2) molecule is effectively determined by the spin angular momentum of a single electron and the orbital motion of the valence electron around the Ca2+ core. An analysis of the Zeeman spectrum as a function of the molecular rotational constant indicates that 2Π3/2 molecules should have significant rotational constants (at least as large as twice the rotational constant of CaF) to be amenable to magnetic trapping in high fields.© 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The system size dependence of electron acceleration during large-scale magnetic island coalescence is studied via a two-dimensional particle-in-cell simulation. Using a simulation box that is larger than those used in previous studies, injection by merging line acceleration and subsequent reacceleration inside a merged island are found to be the mechanisms for producing the most energetic electrons. This finding and knowledge of the reacceleration process enable us to predict that the high energy end of the electron energy spectrum continues to expand as the merged island size increases. Both the merging line acceleration and the reacceleration within a merged island require the island coalescence process to be so dynamic as to involve fast in-flow toward the center of a merged island. Once this condition is met in an early stage of the coalescence, it is likely to stay in the subsequent phase. In other words, if the thin elongated current sheet is initially able to host the dynamic magnetic island coalescence process, it will be a site where repeated upgrades in the maximum energy of electrons occur in a systematic manner. [ABSTRACT FROM AUTHOR]

Design, characterization, and selected applications of a novel electron detector dedicated to conventional perpendicular- and low-angle-incidence conversion electron Mössbauer spectroscopy are presented. The setup is suitable for varying the incident angle and external magnetic fields on Mössbauer source and absorber. Test experiments were performed on α-57Fe films using a conventional single-line 57Co(Rh) and magnetically split, 57Co(α-Fe) Mössbauer sources. The integral “blackness effect” in conversion-electron Mössbauer spectra of 57Fe isotope-enriched absorbers is demonstrated and shown to be pronounced at shallow angles of incidence. In order to determine the alignment and sign of the hyperfine field in an isotope-enriched absorber, the blackness effect is accounted for in a semiempirical way by using single-line source/absorber experimental relative intensities determined independently. This method works with high accuracy for linear polarimetry; however it is only a rough approximation in the case of nearly circular polarimetry. [ABSTRACT FROM AUTHOR]

The University of Manchester Linear System (ULS) [M. G. Rusbridge et al., Plasma Phys. Controlled Fusion 42, 588 (2000)] is an experiment in which a steady-state plasma stream is confined along a longitudinal magnetic field. The plasma passes through a tapered orifice into a separate gas target chamber (GTC) where it interacts with neutral gas at pressures of up to 15 mTorr. The upstream plasma beam is 6–14 mm in diameter with electron temperatures between 2 and 15 eV, and densities in the range of 1017–1019 m-3. The primary aim of this study is to investigate physical processes relevant to gas target divertors in tokamaks. Upstream parameters, in terms of electron temperature and density, can be varied in the ULS enabling the investigation of electron-ion recombination (EIR) or molecular-activated recombination (MAR) processes. Detached recombining plasmas have been studied in the GTC using an axially scanning spectroscopic system with a spatial resolution of less than 5 mm. We have investigated two distinct plasma regimes having the same electron temperature upstream, but upstream densities that differ by an order of magnitude. Vibrationally excited molecules, which are a necessary prerequisite for MAR, have been detected in both these cases. In the higher density case, which ultimately detaches via EIR processes, these excited molecules are present upstream of the EIR region. [ABSTRACT FROM AUTHOR]

Simulations indicate that during flattop current discharges the optimal angles for the aiming of the National Spherical Torus Experiment (NSTX) antennae are quite rugged and basically independent of time. The time development of electron Bernstein wave emission (EBWE) at particular frequencies as well as the frequency spectrum of EBWE as would be seen by the recently installed NSTX antennae are computed. The simulation of EBWE at low frequencies (e.g., 16 GHz) agrees well with the recent preliminary EBWE measurements on NSTX. At high frequencies, the sensitivity of EBWE to magnetic field variations is understood by considering the Doppler broadened electron cyclotron harmonics and the cutoffs and resonances in the plasma. Significant EBWE variations are seen if the magnetic field is increased by as little as 2% at the plasma edge. The simulations for the low frequency antenna are compared to preliminary experimental data published separately by Diem et al. [Rev. Sci. Instrum.77 (2006)] [ABSTRACT FROM AUTHOR]

A microwave ion source is one of the long-life ion sources. In this paper, we report on the characteristics of the extracted Ar ion beam produced by a microwave ion source under various conditions, in terms of magnetic flux distribution and mass flow, and the stability of the ion beam. The measured spectra show that, under the experimental condition, almost all of produced ions were Ar+ ions. For more than 6 h, the ion beam was stable. [ABSTRACT FROM AUTHOR]

Magnetic-field dependent Hall-effect measurements and mobility spectrum analysis were employed to study anisotropic transport in N-polar GaN/Al0.3Ga0.7N heterostructures grown on vicinal sapphire substrates. The significant anisotropy in the mobility in the parallel and perpendicular directions to the miscut direction was accompanied by a slight anisotropy in charge density. A single electron species was found in the direction parallel to the steps resulting from growth on the vicinal substrates; while in the perpendicular direction two distinct electrons peaks were evident at T≤150 K. The lower average mobility in the perpendicular direction is attributed to interface roughness scattering. [ABSTRACT FROM AUTHOR]

We report the spin filling pattern in the few electron limit of silicon metal-on-semiconductor based quantum dots (QDs). Magnetic field dependence of Coulomb oscillation peaks showed filling of parallel spins for the last few electrons. This implies the existence of a large spin exchange energy compared with the orbital level spacing, which has been predicted for relatively large silicon QDs. Our excited-state spectroscopy study confirmed a large spin exchange energy, as well as a large valley splitting at zero magnetic field. [ABSTRACT FROM AUTHOR]

We examine the feasibility of performing single-spin readout in a small quantum dot (SQD), using a quantum point contact (QPC) that is coupled to it by a larger dot with a quasicontinuous spectrum. When the Fermi energy in the QPC is approximately equal to one of the discrete levels of the SQD, a Fano resonance is observed in its conductance. We propose a procedure that uses such Fano peaks to determine the spin projection of a single electron in the SQD, in the presence of an external magnetic field that causes Zeeman splitting of its levels. We also show that this structure can exhibit Rabi oscillations when subject to microwave irradiation. [ABSTRACT FROM AUTHOR]

An experiment is carried out to ascertain the role of energetic electrons in the excitation of plasma turbulence, near the inhomogeneity of a magnetic filter field. This is done in two steps. First, a magnetic filter arrangement is used to eliminate energetic electrons from the plasma. Second, electrons of 0-20 eV energy are deliberately introduced between the main filter and an additional filter located in the target chamber. It is observed that plasma near the additional filter is quiescent in the absence of energetic electrons. When the energetic electrons are introduced, the plasma near the additional filter becomes turbulent. The frequency spectrum of the turbulent fluctuation is broad, with a peak around 100 kHz which lies in the lower hybrid frequency range. [ABSTRACT FROM AUTHOR]

The effect of strongly magnetized electrons on the spectrum of collective electron density fluctuations can be used to measure the magnetic field direction in a plasma with laser light scattering. The application of this method to measure the poloidal field in tokamaks is discussed. It is shown that noncircular beam cross sections will increase the angular resolution without loss in spatial resolution. In experiments to measure the ion temperature this technique results in an increase of scattered power received. The magnetic field direction was measured for the first time in a laboratory plasma using a pulsed CO[sub 2] laser and coherent detection. [ABSTRACT FROM AUTHOR]