An e.s.r. spectrometer operating at 4 mm wavelength for the investigation of large zero field splittings

Abstract

This paper describes the design and construction of an electron resonance spectrometer operating at a wavelength of 4 mm, and with magnetic fields up to 5 T (50 kG). The particular advantages of measurements in this short wavelength band are first discussed, and then the particular problems that arise with these very high frequency microwave components are analysed. It is shown that, despite these difficulties, a spectrometer can be constructed with a sensitivity of 5 x 10 10 spins per millitesla linewidth for an integrating time of 1 s, and that a further improvement of sensitivity by the use of other types of microwave detectors, such as indium antimonide, can be obtained. A series of measurements on myoglobin pastes is then summarized, at the end, to show how such high frequency e.s.r. spectrometers can be employed to measure the large zero field splittings that are produced by the internal molecular fields in certain transition group complexes.