Researchers at NIST have developed a highly sensitive microwave interferometric detection method to measure populations of electron spins in various materials. The technique uses microwave interferometry coupled with microstrip transmission line probes to detect minute impedance changes associated with specific electron spin populations.
The interferometer, based on Mach-Zehnder design, achieves sensitivity of 1 part in 10 million, amplifying changes in the antenna probe with minimal noise. This approach allows detection of smaller ensembles of radiation-induced free radicals than conventional methods, enabling more reliable dosimetry measurements at lower radiation doses.
The technique has also been applied to study microwave conductivity changes in optically generated charges in organic semiconductor films, providing insights into singlet-triplet reaction kinetics and decoherence mechanisms. The method’s simplicity and broad applicability make it suitable for various sample compositions and geometries.
Keywords: electron spin, microwave interferometry, electron spin resonance, dosimetry, radiation-induced free radicals
