Electrical properties of silicon-implanted furnace-annealed silicon-on-sapphire devices

The crystalline quality of s.o.s. layers can be improved near the silicon-sapphire interface by silicon implantation followed by recrystallisation. Device performance on such layers is markedly improved as to n-channel m.o.s.t. noise and leakage current, reverse diode current and lateral bipolar transistor gain. Minority-carrier lifetimes up to 50 ns are deduced

Determination of Exchange Integrals J_1 and J_2 and Magnetic Surface-Anisotropy Energy in EuS from Standing-Spin-Wave Resonance(Physics)

The standing-spin-wave absorption spectrum in thin EuS films has been measured in the temperature interval 1.3-4.2 K. The dependence of the magnetization on temperature has been determined from the ferromagnetic-resonance field and compared with spin-wave theory. The results are well described by the exchange-parameter combination (J_1+J_2)/k_B=(0.096±0.003) K. The temperature dependence of the exchange stiffness parameter D(T) has been calculated including the contribution of a nonzero internal field. The experimental results have been analyzed taking the surface boundary conditions into account and correcting for the temperature and field dependence of H_1. The results show that the apparent temperature dependence of D(T) arises almost entirely from the surface-anisotropy energy. The small observed variation ΔD(T)/D_0 has been analyzed yielding J_2/J_1=-0.57±0.05. The results, expressed as J_1/K_B=(0.214±0.026) K, J_2/k_B=-(0.122±0.025) K are in essential agreement with the inelastic-neutron-scattering determination of Passell et al. but in marked disagreement with Swendsen\u27s Green\u27s-function theory and its application to the calculation of the ferromagnetic and paramagnetic Curie temperature. A comparison with other experimental determinations of J_1 and J_2 is made

Laser annealing of silicon on sapphire

Silicon-implanted silicon-on-sapphire wafers have been annealed by 50-ns pulses from a Q-switched Nd : YAG laser. The samples have been analyzed by channeling and by omega-scan x-ray double diffraction. After irradiation with pulses of a fluence of about 5 J cm^–2 the crystalline quality of the silicon layer is found to be better than in the as-grown state

Mode hopping strongly affects observability of dynamical instability in optical parametric oscillators

Theoretical investigations of dynamical behavior in optical parametric oscillators (OPO) have generally assumed that the cavity detunings of the interacting fields are controllable parameters. However, OPOs are known to experience mode hops, where the system jumps to the mode of lowest cavity detuning. We note that this phenomenon significantly limits the range of accessible detunings and thus may prevent instabilities predicted to occur above a minimum detuning from being evidenced experimentally. As a simple example among a number of instability mechanisms possibly affected by this limitation, we discuss the Hopf bifurcation leading to periodic behavior in the monomode mean-field model of a triply resonant OPO and show that it probably can be observed only in very specific setups.Comment: submitted to Phys. Rev.

A constraint on antigravity of antimatter from precision spectroscopy of simple atoms

Consideration of antigravity for antiparticles is an attractive target for various experimental projects. There are a number of theoretical arguments against it but it is not quite clear what kind of experimental data and theoretical suggestions are involved. In this paper we present straightforward arguments against a possibility of antigravity based on a few simple theoretical suggestions and some experimental data. The data are: astrophysical data on rotation of the Solar System in respect to the center of our galaxy and precision spectroscopy data on hydrogen and positronium. The theoretical suggestions for the case of absence of the gravitational field are: equality of electron and positron mass and equality of proton and positron charge. We also assume that QED is correct at the level of accuracy where it is clearly confirmed experimentally

Precision Optical Measurements and Fundamental Physical Constants

A brief overview is given on precision determinations of values of the fundamental physical constants and the search for their variation with time by means of precision spectroscopy in the optical domain

Generation of Squeezing in Higher Order Hermite-Gaussian Modes with an Optical Parametric Amplifier

We demonstrate quantum correlations in the transverse plane of continuous wave light beams by producing -4.0 dB, -2.6 dB and -1.5 dB of squeezing in the TEM00, TEM10 and TEM20 Hermite- Gauss modes with an optical parametric amplifier, respectively. This has potential applications in quantum information networking, enabling parallel quantum information processing. We describe the setup for the generation of squeezing and analyze the effects of various experimental issues such as mode overlap between pump and seed and nonlinear losses.Comment: 7 pages, 4 figure

Logarithmic two-loop corrections to the Lamb shift in hydrogen

Higher order $(\alpha/\pi)^2 (Z \alpha)^6$ logarithmic corrections to the hydrogen Lamb shift are calculated. The results obtained show the two-loop contribution has a very peculiar behavior, and significantly alter the theoretical predictions for low lying S-states.Comment: 14 pages, including 2 figures, submitted to Phys. Rev. A, updated with minor change

From START to FINISH : the influence of osmotic stress on the cell cycle

Peer reviewedPublisher PD

Zemach and magnetic radius of the proton from the hyperfine splitting in hydrogen

The current status of the determination of corrections to the hyperfine splitting of the ground state in hydrogen is considered. Improved calculations are provided taking into account the most recent value for the proton charge radius. Comparing experimental data with predictions for the hyperfine splitting, the Zemach radius of the proton is deduced to be $1.045(16)$ fm. Employing exponential parametrizations for the electromagnetic form factors we determine the magnetic radius of the proton to be $0.778(29)$ fm. Both values are compared with the corresponding ones derived from the data obtained in electron-proton scattering experiments and the data extracted from a rescaled difference between the hyperfine splittings in hydrogen and muonium