Designing broadband pulsed dynamic nuclear polarization sequences in static solids

TL;DR

This paper introduces novel broadband pulsed DNP sequences using effective Hamiltonian theory, achieving record enhancement factors and broad bandwidths in static solids, thus significantly advancing NMR hyperpolarization techniques.

Contribution

It develops new broadband DNP pulse sequences based on single-spin vector effective Hamiltonian theory, including adiabatic XiX-DNP and BASE experiments, with record enhancement performance.

Findings

Achieved a $^{1}$H DNP enhancement factor of ~360.

Demonstrated a bandwidth about three times the $^{1}$H Larmor frequency (~50 MHz).

Outperformed all previous pulsed DNP sequences at 0.35 T and 80 K.

Abstract

Dynamic nuclear polarization (DNP) is an NMR hyperpolarization technique that mediates polarization transfer from highly polarized unpaired electrons to NMR-active nuclei via microwave (mw) irradiation. The ability to generate arbitrarily shaped mw pulses using arbitrary waveform generators opens up the opportunity to remarkably improve the robustness and versatility of DNP, in many ways resembling the early stages of pulsed NMR. We present here novel design principles based on single-spin vector effective Hamiltonian theory to develop new broadband DNP pulse sequences, namely an adiabatic XiX-DNP experiment and a broadband amplitude modulated signal enhanced (BASE) experiment. We demonstrate that the adiabatic BASE pulse sequence may achieve a DNP $^{1}$H enhancement factor of $\sim$ 360, a record that outperforms all previously known pulsed DNP sequences at $\sim$ 0.35 T and 80 K in static solids. The bandwidth of the BASE-DNP experiments is about 3 times the $^{1}$H Larmor frequency ($\sim$50 MHz).