ENDOR spectroscopy at 275GHz

A multifrequency high-field pulsed electron paramagnetic resonance/electron-nuclear double resonance spectrometer

“…Electron paramagnetic resonance (EPR) experiments have realized new opportunities as magnetic fields have been increased 1,2,3,4,5,6,7 and pulsed capabilities have been added 8,9,10,11,12,13,14 .…”

High-Frequency EPR Instrumentation

“…Obviously, the dimensions decrease as the frequency increases, and its mechanical construction becomes proportionally challenging. Currently, the record is set at 275 GHz, as demonstrated by Schmidt et al [39,82]. The single-mode resonator has the highest possible power conversion ratio.…”

“…A convenient way to adjust the coupling is by rotating the resonator around the waveguide coupling to the iris hole in the cylinder wall. This mode allows a large iris hole, which facilitates the scaling up to higher frequencies [20,28,82]. A specific challenge is to combine the resonator with an ENDOR coil enabling pulse ENDOR applications.…”

“…To allow the RF field to penetrate the resonator, slits are machined in the resonator body. These slits also can serve as optical access [20,82]. At lower frequencies , it has been demonstrated that the resonator cylinder itself can be formed from a ''ribbon coil'' [58].…”

“…This concept will complicate the layout of the bridge considerably, since both RF and LO signals need separate quasi-optical paths. This principle was applied in the pulsed EPR bridge at 275 GHz by Schmidt et al [39,82]. Similar schemes were employed in the multi-frequency bridges operating at 120 and 240 GHz developed by van Tol et al [41,81] and Reijerse et al [42].…”