Theoretical treatment of pulsed Overhauser DNP: consideration of a general periodic pulse sequence
E. A. Nasibulov+*, A. S. Kiryutin+*, A. V. Yurkovskaya+*, H.-M. Vieth+°, K. L. Ivanov+*
+International Tomography Center SB of the RAS, 630090 Novosibirsk, Russia
*Novosibirsk State University, 630090 Novosibirsk, Russia
°Freie Universität Berlin, 14195 Berlin, Germany
Abstract
A general theoretical approach to pulsed Overhauser-type
Dynamic Nuclear Polarization (DNP) is presented. DNP is a powerful
method to create non-thermal polarization of nuclear spins, thereby
enhancing their nuclear magnetic resonance signals. The theory presented can treat
pulsed microwave irradiation of electron paramagnetic resonance
transitions for periodic pulse sequences of general composition. DNP
enhancement is analyzed in detail as a function of the microwave pulse
length for rectangular pulses and pulses with finite rise time.
Characteristic oscillations of the DNP enhancement are found when the
pulse-length is stepwise increased, originating from coherent motion of
the electron spins driven by the pulses. Experimental low-field DNP data
are in very good agreement with this theoretical approach.