FT-EPR WITH A NONRESONANT PROBE - USE OF A TRUNCATED COAXIAL LINE

A truncated transmission line probe (TLP) has been utilized to excite and detect time domain responses after pulsed excitation in electron p aramagnetic resonance (EPR) spectroscopic experiments in the frequency range 200-400 MHz, The TLP device is a modified short-circuited coaxi al line, which allows the irradiation of the sample by the traveling w ave B-1 fields in the frequency range of kilohertz to 30 GHz. In EPR s tudies at 300 MHz carrier frequency, with 10 W incident power, a 45 de grees pulse is 45 ns in duration. This corresponds to a 0.9-G B-1 fiel d, Using the TLP, time-domain responses from the solid N-methyl pyridi nium tetracyanoquinodimethane (TCNQ) were collected at 200, 250, 300, and 350 MHz, with the range limited by the amplifiers. In addition two tubes containing TCNQ placed side-by-side vertically dong the axis of the probe were used to collect time domain responses in the presence of magnetic field gradients to test the feasibility of two-dimensional imaging using a TLP. The magnetic field gradient was steered in the x z plane and 36 projections were collected at 5 degrees intervals, Usin g filtered back-projection image reconstruction, the two-dimensional s patial image in the xz plane was obtained at good resolution. (C) 1998 Academic Press.