Are there charged two-level systems in polymers?

It is shown that a square-root temporal hole broadening found recently in polymethylmethacrylate (PMMA) over a time scale ranging from 103 to 106 s can be explained in the framework of the standard two-level system model with an additional assumption that only a small part (∼10−11) of the two-level system existing in PMMA has a charge.