Positronium as a probe of transient paramagnetic centers in a-SiO2
Abstract
A laser-pump, positron-probe technique has been developed for measuring the dynamics of laser-induced paramagnetic centers in porous materials. The basis of the technique is the fact that the annihilation rate of ortho-positronium may increase in the presence of unpaired spins. By using an intense positron pulse to create positronium atoms in a porous silica sample we have used this effect as a probe to measure the time dependence of the recombination of laser-induced paramagnetic centers. We have observed nonexponential postirradiation decay kinetics extending over ten orders of magnitude that are similar to those previously observed in silica glasses.
- Publication:
-
Physical Review B
- Pub Date:
- February 2007
- DOI:
- 10.1103/PhysRevB.75.085415
- Bibcode:
- 2007PhRvB..75h5415C
- Keywords:
-
- 78.66.Jg;
- 78.40.Fy;
- 78.47.+p;
- 78.70.Bj;
- Amorphous semiconductors;
- glasses;
- Semiconductors;
- Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter;
- Positron annihilation