3.1.1. Effect of UV radiation on virgin hair
Fig. 1a shows the variation of o-Ps lifetime and hence the free
volume size as a function of UV exposure time, while Fig. 1b and
c depict the variation of o-Ps intensity and fractional free volume
respectively. The o-Ps lifetime s3 (and hence Vf) alternately increase
and decrease until 300 h of UV irradiation time and, then,
show a decreasing trend. The fractional free volume (Fv) varies
more or less in a similar manner.