Temperature dependent infrared absorption, crystal-field and intensity analysis of Ce3+ Doped LiYF4

Infrared absorption has been used to determine the crystal-field levels of the 2F7=2 excited multiplet of trivalent cerium doped into scheelite structure LiYF4 single crystals. A crystal-field analysis well accounts for a total of six experimentally observed energy levels and the ground state g-values as previously determined by electron paramagnetic resonance, whilst intensity simulations confirm the experimentally assigned level symmetries. Temperature dependent spectral line broadening measurements highlight the importance of coupling to low frequency phonon modes of the YF8 tetrahedron

The K600 Focal Plane Polarimeter

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Development of an In-Beam Polarimeter for Intermediate Energy Protons Using p+d Elastic Scattering

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

An Absolute Calibration of the p+d High-Energy Polarimeters

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Fiber bundle model with stick-slip dynamics

We propose a generic model to describe the mechanical response and failure of systems which undergo a series of stick-slip events when subjected to an external load. We model the system as a bundle of fibers, where single fibers can gradually increase their relaxed length with a stick-slip mechanism activated by the increasing load. We determine the constitutive equation of the system and show by analytical calculations that on the macro-scale a plastic response emerges followed by a hardening or softening regime. Releasing the load, an irreversible permanent deformation occurs which depends on the properties of sliding events. For quenched and annealed disorder of the failure thresholds the same qualitative behavior is found, however, in the annealed case the plastic regime is more pronounced.Comment: 4 pages, 4 figure

An Energy Feedback System for the MIT/Bates Linear Accelerator

We report the development and implementation of an energy feedback system for the MIT/Bates Linear Accelerator Center. General requirements of the system are described, as are the specific requirements, features, and components of the system unique to its implementation at the Bates Laboratory. We demonstrate that with the system in operation, energy fluctuations correlated with the 60 Hz line voltage and with drifts of thermal origin are reduced by an order of magnitude

Test of a Density-Dependent Effective Interaction Using In-Plane 28-Si(p,p')28-Si Polarization Transfer Measurements

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Investigation of the Effective NN Interaction Through 28-Si(p,p')28-Si Polarization Transfer

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Evidence for Fragmentation of "Stretched" 6- Strength in 28-Si(p,p')28-Si

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Field on Poincare group and quantum description of orientable objects

We propose an approach to the quantum-mechanical description of relativistic orientable objects. It generalizes Wigner's ideas concerning the treatment of nonrelativistic orientable objects (in particular, a nonrelativistic rotator) with the help of two reference frames (space-fixed and body-fixed). A technical realization of this generalization (for instance, in 3+1 dimensions) amounts to introducing wave functions that depend on elements of the Poincare group $G$. A complete set of transformations that test the symmetries of an orientable object and of the embedding space belongs to the group $\Pi =G\times G$. All such transformations can be studied by considering a generalized regular representation of $G$ in the space of scalar functions on the group, $f(x,z)$, that depend on the Minkowski space points $x\in G/Spin(3,1)$ as well as on the orientation variables given by the elements $z$ of a matrix $Z\in Spin(3,1)$. In particular, the field $f(x,z)$ is a generating function of usual spin-tensor multicomponent fields. In the theory under consideration, there are four different types of spinors, and an orientable object is characterized by ten quantum numbers. We study the corresponding relativistic wave equations and their symmetry properties.Comment: 46 page