The use of composite pulses for improving DEER signal at 94GHz

[Display omitted] •Implementation of composite pulses on a home-built 1kW pulsed W-band spectrometer.•Simulation of echoes including B1 profile of the non-resonant sample holder.•Up to 2.7 times echo amplitude enhancement using composite inversion pulses.•1.8 times improvement in DEER SNR for a model nitroxide biradical. The sensitivity of pulsed electron paramagnetic resonance (EPR) measurements on broad-line paramagnetic centers is often limited by the available excitation bandwidth. One way to increase excitation bandwidth is through the use of chirp or composite pulses. However, performance can be limited by cavity or detection bandwidth, which in commercial systems is typically 100–200MHz. Here we demonstrate in a 94GHz spectrometer, with >800MHz system bandwidth, an increase in signal and modulation depth in a 4-pulse DEER experiment through use of composite rather than rectangular π pulses. We show that this leads to an increase in sensitivity by a factor of 3, in line with theoretical predictions, although gains are more limited in nitroxide-nitroxide DEER measurements.