Concentration of atomic hydrogen diffused into silicon in the temperature range 900–1300 °C

Boron-doped Czochralski silicon samples with [B]~1017 cm−3 have been heated at various temperatures in the range 800–1300 °C in an atmosphere of hydrogen and then quenched. The concentration of [H-B] pairs was measured by infrared localized vibrational mode spectroscopy. It was concluded that the solubility of atomic hydrogen is greater than [Hs] = 5.6 × 1018 exp( − 0.95 eV/kT)cm−3 at the temperatures investigated

A Survey for Outer Satellites of Mars: Limits to Completeness

We surveyed the Hill sphere of Mars for irregular satellites. Our search covered nearly the entire Hill Sphere, but scattered light from Mars excluded the inner few arcminutes where the satellites Phobos and Deimos reside. No new satellites were found to an apparent limiting red magnitude of 23.5, which corresponds to radii of about 0.09 km using an albedo of 0.07.Comment: 5 figures (1 color), 2 Tables, to appear in AJ Nov. 200

Terahertz amplification in delta-doped germanium films with in-plane transport

Amplification of terahertz radiation on intersubband transitions has been analyzed by numerical Monte Carlo simulation for p-type delta-doped Ge films with in-plane transport configuration of applied electric and magnetic fields. A significant increase of the gain is found, compared to existing bulk p-Ge lasers, due to spatial separation of light and heavy hole streams, which reduces scattering of light holes on ionized impurities and heavy holes. The considered device has potential as a widely tunable (2-4 THz) laser with high duty cycle and operating temperatures up to 50 K

Terahertz gain on intersubband transitions in multilayer delta-doped p-Ge structures

A far-infrared laser concept based on intersubband transitions of holes in p-type periodically delta-doped semiconductor films is studied using numerical Monte Carlo simulation of hot-hole dynamics. The considered device consists of monocrystalline pure Ge layers periodically interleaved with delta-doped layers and operates with vertical hole transport in the presence of an in-plane magnetic field. Population inversion on intersubband transitions arises due to light-hole accumulation in E perpendicular to B fields, as in the bulk p-Ge laser. However, the considered structure achieves spatial separation of hole accumulation regions from the doped layers, which reduces ionized-impurity and carrier-carrier scattering for the majority of light holes. This allows a remarkable increase of the gain in comparison with bulk p-Ge lasers. Population inversion and gain sufficient for laser operation are expected up to 77 K. Test structures grown by chemical-vapor deposition demonstrate feasibility of producing the device with sufficient active thickness to allow quasioptical electrodynamic cavity solutions

Site-Selective Spectroscopy And Crystal-Field Analysis For Nd3+ In Strontium Fluorovanadate

Site‐selective spectroscopy reveals that Nd3+ ions occupy more than 40 different crystal‐field environments in Sr5(VO4)3F. Preferential energy transfer to the site responsible for 1 μm lasing occurs but becomes less complete with increasing temperature. The 4I and 4F3/2 Stark levels of the lasing site have been determined and an analysis of the crystal field performed. From the crystal‐field fitting parameters Bkq, a calculated energy‐level spectrum is determined up to 17 500 cm−1 with a rms deviation from the available experimental levels of 6 cm−1

The potential for tidally heated icy and temperate moons around exoplanets

Moons of giant planets may represent an alternative to the classical picture of habitable worlds. They may exist within the circumstellar habitable zone of a parent star, and through tidal energy dissipation they may also offer alternative habitable zones, where stellar insolation plays a secondary, or complementary, role. We investigate the potential extent of stable satellite orbits around a set of 74 known extrasolar giant planets located beyond 0.6 AU from their parent stars - where moons should be long-lived with respect to removal by stellar tides. Approximately 60% of these giant planets can sustain satellites or moons in bands up to $\sim 0.04$ AU in width. For comparison, the Galiean satellites extend to $\sim 0.013$ AU. We investigate the stellar insolation that moons would experience for these exoplanet systems, and the implications for sublimation loss of volatiles. We find that between 15 and 27% of {\em all} known exoplanets may be capable of harboring small, icy, moons. In addition, some 22-28% of all known exoplanets could harbor moons within a ``sublimation zone'', with insolation temperatures between 273 K and 170 K. A simplified energy balance model is applied to the situation of temperate moons, maintained by a combination of stellar insolation and tidal heat flow. We demonstrate that large moons ($>0.1$M$_{\oplus}$), at orbital radii commensurate with those of the Galilean satellites, could maintain temperate, or habitable, surface conditions during episodes of tidal heat dissipation of the order 1-100 times that currently seen on Io. (Abridged).Comment: 28 pages, 8 Figures, AASTex, Accepted for publication in the Astrophysical Journa

Precession of a Freely Rotating Rigid Body. Inelastic Relaxation in the Vicinity of Poles

When a solid body is freely rotating at an angular velocity ${\bf \Omega}$, the ellipsoid of constant angular momentum, in the space $\Omega_1, \Omega_2, \Omega_3$, has poles corresponding to spinning about the minimal-inertia and maximal-inertia axes. The first pole may be considered stable if we neglect the inner dissipation, but becomes unstable if the dissipation is taken into account. This happens because the bodies dissipate energy when they rotate about any axis different from principal. In the case of an oblate symmetrical body, the angular velocity describes a circular cone about the vector of (conserved) angular momentum. In the course of relaxation, the angle of this cone decreases, so that both the angular velocity and the maximal-inertia axis of the body align along the angular momentum. The generic case of an asymmetric body is far more involved. Even the symmetrical prolate body exhibits a sophisticated behaviour, because an infinitesimally small deviation of the body's shape from a rotational symmetry (i.e., a small difference between the largest and second largest moments of inertia) yields libration: the precession trajectory is not a circle but an ellipse. In this article we show that often the most effective internal dissipation takes place at twice the frequency of the body's precession. Applications to precessing asteroids, cosmic-dust alignment, and rotating satellites are discussed.Comment: 47 pages, 1 figur

Injection-seeded internal-reflection-mode p-Ge laser exceeds 10 W peak terahertz power

Injection seeding of a large active p-Ge laser crystal operating on total internal reflection modes is demonstrated with peak output power at the level of 40 W in the 1.5-4.2 THz spectral range. The improvement over traditional 1 W axial mode p-Ge lasers is due both to spatially and temporally more efficient use of the available population inversion

Pulse separation control for mode-locked far-infrared p-Ge lasers

Active mode locking of the far-infrared p-Ge laser giving a train of 200 ps pulses is achieved via gain modulation by applying an rf electric field together with an additional bias at one end of the crystal parallel to the Voigt-configured magnetic field. Harmonic mode locking yields a train of pulse pairs with variable time separation from zero to half the roundtrip period, where pulse separation is electrically controlled by the external bias to the rf field