Controlling Effective Hamiltonians: Broadband Pulsed Dynamic Nuclear Polarization by Constrained Random Walk and Non-linear Optimization

TL;DR

This paper introduces a novel method combining constrained random walk and non-linear optimization to design broadband DNP pulse sequences, enhancing control over effective Hamiltonians for magnetic resonance.

Contribution

It develops a systematic approach for designing broadband polarization transfer sequences using constrained random walk and FOM-based optimization, advancing magnetic resonance control techniques.

Findings

Designed broadband DNP pulse sequences with 100 MHz electron spin excitation bandwidth.

Demonstrated the effectiveness of combined cRW and FOM optimization in magnetic resonance.

Provided a fundamental understanding of effective Hamiltonian control in DNP experiments.

Abstract

We present constrained random walk (cRW) and figure of merit (FOM) based non-linear optimization procedures for systematic design and fundamental understanding of magnetic resonance experiments dressing bilinear and linear effective Hamiltonians to provide broadband polarization transfer. cRW can be used directly for fast random experiment design, or in combination with non-linear optimization or optimal control, leveraging the optimization of a FOM function for efficient control of linear and bilinear terms derived by exact effective Hamiltonian theory (EEHT). The efficacy of the combined cRW and FOM-based optimization approach is demonstrated by the design of broadband dynamic nuclear polarization (DNP) pulse sequences for static solids with an electron spin excitation bandwidth reaching 100 MHz.