RESUMO
The construction and performance of a cryogenic 35GHz pulse electron nuclear double resonance (ENDOR) probehead for large samples is presented. The resonator is based on a rectangular TE(102) cavity in which the radio frequency (rf) B(2)-field is generated by a two turn saddle ENDOR coil crossing the resonator along the sample axis with minimal distance to the sample tube. An rf power efficiency factor is used to define the B(2)-field strength per square-root of the transmitted rf power over the frequency range 2-180MHz. The distributions of the microwave B(1)- and E(1)-field, and the rf B(2)-field are investigated by electromagnetic field calculations. All dielectrics, the sample tube, and coupling elements are included in the calculations. The application range of the probehead and the advantages of using large sample sizes are demonstrated and discussed on a number of paramagnetic samples containing transition metal ions.