Nonphotochemical hole burning of organic dyes and rare earth ions in polymers and glasses: a probe of the amorphous state

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Fearey, Bryan
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The Department of Chemistry seeks to provide students with a foundation in the fundamentals and application of chemical theories and processes of the lab. Thus prepared they me pursue careers as teachers, industry supervisors, or research chemists in a variety of domains (governmental, academic, etc).

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New and in depth studies of amorphous materials (e.g., glasses and polymers) probed via the low temperature optical technique of nonphotochemical hole burning NPHB are presented. An extensive review of the phenomena itself, along with selected topics involving the use of persistent hole burning techniques, is given. In addition, a semi-complete tabulation of essentially all hole burning systems to date is included;The deuteration dependence in an amorphous host is examined for the system of tetracene in an ethanol/methanol mixture. The results illustrate the importance of hydrogen bonding in the hole burning process;The discovery of a highly efficient (or facile) class of hole burning systems, i.e., ionic dyes in hydroxylated polymers (i.e., poly(vinyl alcohol) PVOH and poly(acrylic acid) PAA ), is presented and discussed. Ultrafast relaxation processes (i.e., dephasing) are studied for the system of cresyl violet perchlorate CV in PVOH. Further, for the first time, NPHB of rare earth ions, specifically Pr('+3) and Nd('+3), in a soft organic glass (i.e., PVOH) is discussed briefly;Detailed experimental results of two related phenomena, spontaneous hole filling SPHF and laser induced hole filling LIHF , are presented and discussed for several systems: rhodamine 560 perchlorate R560 , rhodamine 640 perchlorate R640 , CV, Pr('+3) and Nd('+3) in either PVOH or PAA. A theoretical model is developed for SPHF. The model invokes a correlated feedback mechanism from the anti-hole, which is able to account for the fact that no line broadening is observed;A tentative model is also presented for the phenomenon of LIHF. Again note that there is no hole broadening. Several mechanisms (i.e., bulk heating, anti-hole reversion and energy transfer) are argued to be insignificant. The actual model involves the concept of global spectral diffusion, which allows for long range interactions between both spectrally and spatially removed sites. This long range communication is suggested to occur between distinct extrinsic two level systems TLS (impurity coupled TLS) through intrinsic TLS (host TLS) via a reptation type motion. The additional ingredient invoked to account for the frequency dependence of LIHF is a correlation (either positive or negative) between the absolute;energy of the glassy state (i.e., the set of intrinsic TLS) and the transition energy of the impurity; *DOE Report IS-T-1207. This work was performed under Contract W-7405-eng-82 with the U.S. Department of Energy.

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Wed Jan 01 00:00:00 UTC 1986