14 N Fourier Transform Nuclear Quadrupole Resonance. Instrumentation: Measurements on Cyanuric Chloride

A Matec pulsed instrument, already equipped with a laboratory-built data system, has been considerably improved by adding new capabilities, such as versatile pulse sequence programming. Among other things, this allows automated T 1 relaxation measurements. The instrument has been employed to record the 14 N NQR FT spectrum of cyanuric chloride and measure its T 1 relaxation time from 77 K to the melting point at 418 K. The four-line 14 N spectrum indicates the presence of two chemically inequivalent sites. The intensity ratio of the lines identifies the site pertaining to a couple of symmetry-related 14 N nuclei. The lines smoothly decrease in frequency up to the melting point, where they remain narrow and almost equally spaced. Considering previous results at 4.2 K, this indicates that a single phase is stable over the entire accessible temperature range. The relaxation time T 1 decreases smoothly with increasing temperature, with a T -2 law, from nearly 180 s at 77 K to about 1 s near the melting point, where a precipitous decrease starts. The high T 1 values found are consistent with the lack of nuclei having high magnetic moment.