2-DIMENSIONAL NQR SEPARATION OF INHOMOGENEOUS AND HOMOGENEOUS LINESHAPES IN DISORDERED SOLIDS

A two-dimensional (2D) zero field NQR separation of inhomogeneous and homogeneous lineshapes technique is described. The nuclear spin Hamilt onian for spins I > 1/2 in zero magnetic field consists to a good appr oximation only of the electric quadrupole term. The 2D separation tech nique enables a separate spectroscopic observation of a static and a r andomly time-fluctuating dynamic part of the quadrupole interaction. T he separation is based on the fact that nuclear spin precession under a static quadrupolar Hamiltonian can be time-reversed whereas this can not be achieved under the action of a randomly time-fluctuating Hamil tonian. The 2D spectrum displays in the omega2-domain the inhomogeneou sly broadened lineshape, which is a convolution of the inhomogeneous s tatic frequency distribution function and the homogeneous (adiabatic) lineshape. The omega1-domain shows the pure homogeneous lineshape. A d econvolution of the inhomogeneous lineshape with the homogeneous one y ields a pure static inhomogeneous frequency distribution function whic h is characteristic and theoretically known for many different models of disordered solids like glasses and incommensurate systems. This tec hnique is important in studies where both lineshapes have comparable w idths. The 2D NQR separation technique has been applied to As-75 in a proton glass Rb0.98(NH4)0.02H2AsO4.