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CP: Chemische Physik

CP 5: Spektroskopie

CP 5.2: Vortrag

Montag, 22. März 1999, 10:00–10:15, Gg

Long-time scale spectral diffusion in PMMA: Beyond the TLS model ? — •O.V. Khodykin¹, J. M"uller¹, W. Richter¹, D. Haarer¹, and B.M. Kharlamov² — ¹Physikalisches Institut, Universit"at Bayreuth, 95440 Bayreuth — ²Institute of Spectroscopy, Russian Academy of Sciences, Troitzk, Russia

Spectral diffusion (SD) in PMMA doped with H₂-TBP is investigated at 4.2 K on a time scale 2÷ 10⁶s via optical hole burning. Two contradictory (in frames of TLS model) results are obtained. The first is the absence of aging effects which put the upper limit for the TLS relaxation times to tens of minutes. The second one is an intensive superlogarithmic SD on the whole time scale of the experiment, which evidences the presence of very slow relaxations, independent of the sample history on the time scale up to 2 months. The presented results provide the clear evidence of the deviation of SD behavior from the TLS model predictions at moderate low temperatures. The concept of structural relaxations is applied for a qualitative interpretation of the experimental data.