Higher sensitivity measurement is feasible by using a Gunn oscillator which supplies a noiseless stable microwave, a TE011 cylindrical cavity with a high Q-value, a large sample volume, and a modulation coil capable of obtaining a homogeneous magnetic field. The ESR spectrum above, obtained for Tempol/ Benzene solution (1 uM), by using a 100 kHz modulation frequency, clearly shows a guaranteed sensitivity of 5.0x109 spins/0.1 mT.
The magnet polepiece is made of a high-purity material which is precision machined and provides for a homogeneous magnetic field. Ring shims are attached to polepiece surfaces to allow use of a wide high-homogeneity range. In order to obtain high resolution, a cavity made of materials without impurities such as ferromagnetic material, a highly stable power supply for the magnet, and stable magnetic field modulation are required, besides the magnet with a homogeneous magnetic field.
The JES-X330 is well designed to meet these requirements. Shown above is an ESR spectrum of Coppinger radical. The smallest split coupling of t-butyl base 4.7 uT, and its split shows a 2.35 uT resolution.
In order to obtain data with excellent reproducibility, a stable and linear magnetic field is necessary. To obtain a stabilized static magnetic field, the JES-X330 employs a Hall element with good linearity, and the entire Hall element is thermally controlled to guarantee a magnetic field stability as high as 5 x 10-6 / 0C・h. The high stability shown is 100 times superimposed ESR spectra of perylene cation radical with ±0.1 mT magnetic field sweep in one hour measurement.