[1] Polymer Materials and Radiation Group,
[2] Department of Chemistry,undefined
[3] University of Queensland,undefined
[4] QLD 4072,undefined
[5] Australia e-mail: hill@chemistry.uq.edu.au,undefined
[6] Fax: +61 7 3365 4299,undefined
[7] Centre for Magnetic Resonance,undefined
[8] University of Queensland,undefined
[9] QLD 4072,undefined
[10] Australia,undefined