The effect of high pressure on the dynamics of doped organic glasses: A study by spectral hole-burning

T. M. H. Creemers, J. M. A. Koedijk, I. Y. Chan, R. J. Silbey, S. Völker
1997 Journal of Chemical Physics  
We report time-resolved spectral hole-burning experiments on bacteriochlorophyll-a ͑BChl-a͒ doped into the glass triethylamine ͑TEA͒ at ambient pressure (⌬pϭ0) and at a pressure of ⌬ p ϭ3.4 GPa. We observe a number of remarkable effects: ͑a͒ from the change in the temperature dependence of the "effective" optical homogeneous linewidth ⌫ hom Ј , we conclude that local order is introduced in TEA under high pressure; ͑b͒ from the change in the time dependence of ⌫ hom Ј , we conclude that spectral
more » ... diffusion is induced by "downhill" energy transfer among BChl-a molecules ͑at a concentration of cϳ5ϫ10 Ϫ4 M͒ within the S 1 ↔S 0 0-0 band, both at ambient and high pressure; and ͑c͒ from the wavelength dependence of ⌫ hom Ј , we conclude that an energy barrier (⌬Eϳ135 cm Ϫ1 at ⌬pϭ0, and ⌬Eϳ70 cm Ϫ1 at ⌬ pϭ3.4 GPa͒ has to be crossed in order to excite two-level systems ͑TLSs͒ of the TEA host which, subsequently, leads to spectral diffusion. We present a qualitative molecular model for the interpretation of these effects.
doi:10.1063/1.474843 fatcat:bhwd3sq72jggnjbicx7hex233m