Abstract. The dual technique magnetometer system onboard the Cassini orbiter is described. This instrument consists of vector helium and fluxgate magnetometers with the capability to operate the helium device in a scalar mode. This special mode is used near the planet in order to determine with very high accuracy the interior field of the planet. The orbital mission will lead to a detailed understanding of the Saturn/Titan system including measurements of the planetary magnetosphere, and the interactions of Saturn with the solar wind, of Titan with its environments, and of the icy satellites within the magnetosphere.

Abstract. The dual technique magnetometer system onboard the Cassini orbiter is described. This instrument consists of vector helium and fluxgate magnetometers with the capability to operate the helium device in a scalar mode. This special mode is used near the planet in order to determine with very high accuracy the interior field of the planet. The orbital mission will lead to a detailed understanding of the Saturn/Titan system including measurements of the planetary magnetosphere, and the interactions of Saturn with the solar wind, of Titan with its environments, and of the icy satellites within the magnetosphere.

For more than 40 years it was thought that polaron-and exciton-phonon systems exhibited unexpected localization properties. Particular attention was paid to the so-called phonon-induced self-trapping transition, which, it was believed, should manifest itself as a point of nonanalyticity in the ground-state energy as a function of the electron-phonon coupling parameter. It will be demonstrated for a large class of (generalized Frohlich) models that no such transition exists. The dimensionality of space has no qualitative influence; insofar, an application of the authors' results to problems in lower dimensions (e.g., polarons in quantum wells) is straightforward. The same holds true if homogeneous external fields are involved; for example, a discontinuous mass stripping for magnetopolarons can be excluded. On the other hand, a phase-transition-like behavior will be found, if a polaron or exciton is exposed to a short-range potential, allowing a so-called pinning transition. The authors emphasize, however, that even in this case the transition is only modified, and not induced, by phonons.

No abstract

We consider a model describing the one-dimensional confinement of an exciton in a symmetrical, rectangular quantum-well structure and derive upper and lower bounds for the binding energy E b of the exciton. Based on these bounds, we study the dependence of E b on the width of the confining potential with a higher accuracy than previous reports. For an infinitely deep potential the binding energy varies as expected from 1 Ry at large widths to 4 Ry at small widths. For a finite potential, but without consideration of a mass mismatch or a dielectric mismatch, we substantiate earlier results that the binding energy approaches the value 1 Ry for both small and large widths, having a characteristic peak for some intermediate size of the slab. Taking the mismatch into account, this result will in general no longer be true. For the specific case of a Ga 1−x Al x As/GaAs/Ga 1−x Al x As quantum-well structure, however, and in contrast to previous findings, the peak structure is shown to survive.