Spin coherence effects in the electron—nuclear polarization transfer process

✍ Scribed by V. Macho; D. Stehlik; H.-M. Vieth

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 470 KB
• Volume: 180
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(91)85139-n

✦ Synopsis

The nuclear spin polarization resulting from optical pumping of molecular triplet states, ONP, has been studied in a timeresolving experiment by synchronized irradiation of light and rfpulses. After laser flash excitation of T, triplet states of actidine doped into a fluorene crystal, an rf pulse of variable intensity and duration is applied near the resonance of an electronic spin transition. It leads to partial transfer of optically generated electronic polarization to the nuclear spin reservoir (rf-ONP). For sufficiently high if-intensity, the polarization transfer shows an oscillatory behaviour when varying the pulse length in the submicrosecond range, which reflects the initial coherence among the spins. Critical tests for the analysis are provided by experiments under different rfexcitation conditions and for various isotopic compositions. The transfer process is shown to involve two steps on different time scales, the first of which is closely related to nutations of electron spins about the rotating& field.