2D EXCHANGE NQR SPECTROSCOPY

In nuclear magnetic resonance (NMR), two-dimensional (2D) spectroscopy has proven to be a versatile tool for the investigation of exchange p athways. II is shown that analogous experiments can be performed with pure nuclear quadrupole resonance (NQR). A theoretical treatment of th e 2D exchange NQR pulse sequence is presented on the basis of the fict itious 1/2 formalism. Systems with powder geometry are considered in p articular. The demands specific for NQR are discussed in comparison wi th the NMR case. Appropriate test experiments refer to Cl-35 quadrupol e resonances of chloroform and p-chlorobenzotrichloride. Exchange proc esses by rotational jumps and molecular reorientations between sites w ith different electric field gradient tensors are shown to reveal them selves by off-diagonal peaks in the 2D spectra, provided that the righ t ranges of temperature and mixing times are used.