Search results for "ACTIVATION"

Influence of boron on donor–acceptor pair recombination in type IIa HPHT diamonds

2013

Abstract We report on the investigation of donor–acceptor pair (DAP) and free carrier recombination in HPHT IIa type diamonds and determination of boron concentration by differential transmittivity (DT) technique. Photoluminescence and photoluminescence excitation spectra were measured in 8–300 K temperature range and provided a broad (~ 0.67 eV) Gaussian DAP band which peaked at 2.2 eV at low temperatures, while above 200 K it sharply shifted to 2.5 eV and became more intense. Thermoluminescence measurements also demonstrated a similar tendency. This peculiarity was explained by DAP recombination between the nitrogen and the boron, the latter being in the ground and the excited states at l…

1983

On the stability of bifurcation branches in thermal ignition

1984

A method is given to determine the stability of stationary solutions of the thermal ignition equation for the case ofn-dimensional spherical symmetry, together with the number of unstable modes. For sufficiently high temperature and activation temperature this number is arbitrarily large. Some numerical results on the solutions and their stability are reported.

NH3 dynamics in Zn(NH3)4I2 and Zn(NH3)4Br2 investigated by incoherent quasielastic neutron scattering

1997

We report on studies of NH3 dynamics in Zn(NH3)4I2 and Zn(NH3)4Br2 by means of incoherent quasielastic neutron scattering in the temperature range from 150 to 300 K. Quasielastic experiments were carried out on the Fermi chopper time-of-flight spectrometer at NIST. The Lorentzian full-widths at half-maximum, ƒw, of the quasielastic line follow an Arrhenius law and increase from 0.39 [0.25] meV at 150 K to 1.33 [0.80] meV at 300 K. We find an activation energy Ea for the NH3 reorientations of 32(1) and 30(3) meV for Zn(NH3)4I2 and Zn(NH3)4Br2, respectively.

Vortex-liquid entanglement inBi2Sr2CaCu2O8+δfilms in the presence of quenched disorder

1998

We have investigated the thermally activated behavior of the in-plane electrical resistivity of ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$ films for magnetic fields $Bl~{10}^{4}\mathrm{G}$ applied parallel to the $c$ axis. The activation energy in the vortex-liquid state changes suddenly at a crossover field ${B}_{\mathrm{cr}}.$ The anisotropy reduction generated by oxygen annealing leads to the increase of the crossover field. For $Bl{B}_{\mathrm{cr}},$ the activation energy $U$ is weakly magnetic-field dependent. For $Bg{B}_{\mathrm{cr}},$ $U(B,T)\ensuremath{\sim}(1\ensuremath{-}{T/T}_{c0}{)/B}^{1/2},$ which corresponds to an entan…

Determination of the Bi209(n,γ)Bi210g cross section using the NICE detector

2021

The capture cross section of $^{209}\mathrm{Bi}(n,\ensuremath{\gamma})^{210g}\mathrm{Bi}$ was measured at different astrophysically relevant energies including thermal capture cross section (25 meV), resonance integral, and the Maxwellian averaged cross section at a thermal energy of $kT=30$ keV. The partial capture cross section $({\ensuremath{\sigma}}_{g})$ was determined using the activation technique and by measuring the $^{210}\mathrm{Po}$ activity. The newly developed and tested NICE detector setup was used to measure the $\ensuremath{\alpha}$ activity of the $^{210}\mathrm{Po}$. Using this setup the thermal and resonance integral cross sections were determined to be $16.2\phantom{\ru…

Study of the 2n-evaporation channel in the 4,6He+206,208Pb reactions

2009

Abstract Excitation functions of the reaction products were measured for the reactions induced by 4,6 He projectiles on 208,206 Pb targets, leading to the same compound nucleus. This was accomplished by using the stacked-foil activation technique. The identification of the reaction products (accumulated in the Pb targets) was done by their radioactive α -decays. The excitation functions for the various products were obtained at energies including the sub-Coulomb barrier region. A large value of the fusion cross section was observed in the case of the reaction induced by the weakly bound 6 He projectile.

Noise-induced effects in nonlinear relaxation of condensed matter systems

2015

Abstract Noise-induced phenomena characterise the nonlinear relaxation of nonequilibrium physical systems towards equilibrium states. Often, this relaxation process proceeds through metastable states and the noise can give rise to resonant phenomena with an enhancement of lifetime of these states or some coherent state of the condensed matter system considered. In this paper three noise induced phenomena, namely the noise enhanced stability, the stochastic resonant activation and the noise-induced coherence of electron spin, are reviewed in the nonlinear relaxation dynamics of three different systems of condensed matter: (i) a long-overlap Josephson junction (JJ) subject to thermal fluctuat…

EFFECTS OF COLORED NOISE IN SHORT OVERDAMPED JOSEPHSON JUNCTION

2008

We investigate the transient dynamics of a short overdamped Josephson junction with a periodic driving signal in the presence of colored noise. We analyze noise induced henomena, specifically resonant activation and noise enhanced stability. We find that the positions both of the minimum of RA and maximum of NES depend on the value of the noise correlation time tau_c. Moreover, in the range where RA is observed, we find a non-monotonic behavior of the mean switching time as a function of the correlation time tau_c.

Measurement of the Pu-242(n,gamma) cross section from thermal to 500 keV at the Budapest research reactor and CERN n_TOF-EAR1 facilities

2019

The design and operation of innovative nuclear systems requires a better knowledge of the capture and fission cross sections of the Pu isotopes. For the case of capture on 242Pu, a reduction of the uncertainty in the fast region down to 8-12% is required. Moreover, aiming at improving the evaluation of the fast energy range in terms of average parameters, the OECD NEA High Priority Request List (HPRL) requests high-resolution capture measurements with improved accuracy below 2 keV. The current uncertainties also affect the thermal point, where previous experiments deviate from each other by 20%. A fruitful collaboration betwen JGU Mainz and HZ Dresden-Rossendorf within the EC CHANDA project…