Effect of hydrostatic pressure on irreversible thermal transformations in a polymer glass at low temperatures (original) (raw)

Irreversible broadening of spectral holes in chlorin-doped polystyrene glass was studied for the first time in the temperature cycling experiments under high pressure (by raising the temperature from 5 K to various magnitudes up to 18 K and turning back to 5 K at several fixed pressures between 0 and 5 kbar). At all pressures the increment in the hole width observed after completing a temperature cycle exhibits a slightly superlinear (proportional to T to the power 3/2) dependence on the cycling temperature. The magnitude of this increment is essentially reduced under high pressure (e.g., at 4.9 kbar it makes up less than 2/3 of its initial value obtained at ambient pressure). The residual broadening of holes is interpreted as a result of irreversible thermally induced spectral diffusion arising from interaction of the electronic transition in a dopant molecule with two-level systems (TLSs) which perform thermally activated overbarrier jumps between two possible states of a TLS. The...