Optical detection and electronic simulation of magnetic resonance in zero magnetic field of dihydroporphin free base

Abstract

An apparatus for the measurement of optically detected magnetic resonance (ODMR) in zero magnetic field at 4.2 K using commercially available parts is described. A simple electronic analogue device is used to obtain kinetic data from ODMR transients in a fast and reliable way. From these data decay rates of the three spin levels of the lowest molecular triplet state can be obtained, whereas populating rates can be determined within defined limits. Since the apparatus is suited for unguarded operation during long periods of time, signal averaging of weak signals, e.g., from biological molecules, is particularly easy. Kinetic data have been obtained for dihydroporphin, which can be considered as the structural basis for chlorophyll: k₁= 121±12 sec⁻¹; k₂=277±28 sec⁻¹; k₃=22±2 sec⁻¹; 0.28<P₁P₂=1; P₃k_i and P_i are the decay and populating rates of the ith spin level.