Pressure induced spectral diffusion as investigated by linewidth studies of polymers doped with dye molecules

Photochemical hole burning at 1.5 K was used to study the influence of uniaxial pressure on the homogeneous line profile of the S₁←S₀ transition of free base phthalocyanine in polyethylene (PE) and polymethylmethacrylate (PMMA) matrices. The line profiles which were observed show already at pressure changes which were as small as 100 hPa substantial broadening effects. At higher pressures of up to 3 x 10⁴ hPa we observed irreversible line broadening phenomena, which we attribute to irreversible site changes of the host-guest system.