Title:Oral: Optimizing EPR pulses for broadband excitation and refocusing

Pulse electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for characterizing nanoscale systems with unpaired electrons. We present numerically optimized broadband pulse shapes that maximize the Hahn echo amplitude from a spin-½ system. Pulse shapes are parameterized as neural networks, nonlinear amplitude-limited Fourier series, and discrete time series. These are compared to an optimized choice of the conventional hyperbolic secant pulse shape. During the optimization, we include practically relevant aspects such as limited power, power amplifier nonlinearity and the transfer function of the microwave resonator. We show that these numerically optimized pulse shapes yield a 10% improvement of the Hahn echo amplitude over the known optimal hyperbolic secant pulse shapes. We also discuss potential applications of numerical optimized pulse shapes to a more complex coupled two-spin system to infer the inter-spin distance.