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New Frontiers in Sensitivity for EPR Spectroscopy:

From Biological Cells to Nano Materials

Rectangular shaped pulses which are, with only few exceptions, the only used in pulsed EPR exhibit insufficient and unselective excitation profiles. First aim of this project is to enhance the excitation bandwidth achievable with a given microwave power by amplitude and phase modulation. We therefore implemented an ultrafast microwave modulator with a horizontal resolution of 1 ns in our Bruker pulsed X Band Spectrometer. The optimization of these new pulses is done by collaborating groups in Germany (Prof. Steffen Glaser, TU Munich) and in the US (Prof. Thomas Skinner, Wright State University).

Comparison of a conventional rectangular pulse (left column) and the optimized pulse, which we call BEBOP (Broadband Exciation By Optimized Pulses). The panels in the first row show the pulse shapes. The panels in the second row (b, b') show the simulated magnitude of the excited transverse magnetization. The black curves in the third row (c, c') represent the simulated magnitude of the transverse magnetization multiplied by the measured frequency response of the video amplifier. The grey lines in c and c' represent experimental magnitude-mode spectra.