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Title: High-pressure optical studies

High pressure experimentation may concern intrinsically high pressure phenomena, or it may be used to gain a better understanding of states or processes at one atmosphere. The latter application is probably more prevelant in condensed matter physics. Under this second rubric one may either use high pressure to perturb various electronic energy levels and from this pressure tuning characterize states or processes, or one can use pressure to change a macroscopic parameter in a controlled way, then measure the effect on some molecular property. In this paper, the pressure tuning aspect is emphasized, with a lesser discussion of macroscopic - molecular relationships. In rare earth chelates the efficiency of 4f-4f emission of the rare earth is controlled by the feeding from the singlet and triplet levels of the organic ligand. These ligand levels can be strongly shifted by pressure. A study of the effect of pressure on the emission efficiency permits one to understand the effect of ligand modification at one atmosphere. Photochromic crystals change color upon irradiation due to occupation of a metastable ground state. In thermochromic crystals, raising the temperature accomplishes the same results. For a group of molecular crystals (anils) at high pressure, the metastable state canmore » be occupied at room temperature. The relative displacement of the energy levels at high pressure also inhibits the optical process. Effects on luminescence intensity are shown to be consistent. In the area of microscopic - molecular relationships, the effect of viscosity and dielectric properties on rates of non-radiative (thermal) and radiative emission, and on peak energy for luminescence is demonstrated. For systems which can emit from either of two excited states depending on the interaction with the environment, the effect of rigidity of the medium on the rate of rearrangement of the excited state is shown.« less
Authors:
Publication Date:
OSTI Identifier:
6463895
Report Number(s):
DOE/ER/01198-1359; CONF-810828-1
ON: DE81025577; TRN: 81-014016
DOE Contract Number:
AC02-76ER01198
Resource Type:
Conference
Resource Relation:
Conference: Conference on high pressure physics, Bad Honnef, F.R. Germany, Aug 1981
Research Org:
Illinois Univ., Urbana (USA). School of Chemical Sciences
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CRYSTAL LATTICES; OPTICAL PROPERTIES; RARE EARTH COMPOUNDS; ELECTRONIC STRUCTURE; CHELATES; EMISSION SPECTRA; ENERGY-LEVEL TRANSITIONS; METASTABLE STATES; PRESSURE DEPENDENCE; VERY HIGH PRESSURE; COMPLEXES; CRYSTAL STRUCTURE; ENERGY LEVELS; EXCITED STATES; PHYSICAL PROPERTIES; SPECTRA 360602* -- Other Materials-- Structure & Phase Studies; 656000 -- Condensed Matter Physics