N-14 NQR STUDY ON REORIENTATIONAL MOTION IN A MIXED SYSTEM [(CH2)(6)N-4](1-X)[KNO2](X)

Temperature dependences of N-14 NQR frequency and spin-lattice relaxat ion time (T-1) have been investigated in a mixed system [(CH2)(6)N-4]( 1-x)[KNO2](x). From T-1 measurement, the activation energy (E-a) on re orientational motion above 270 K in the pure (CH2)(6)N-4 is determined to be E-a = 15.1 kcal mole(-1), in agreement with a previous report. The E-a determined in the mixed system [(CH2)(6)N-4](1-x)[KNO2](x) wit h x = 0.06, 0.13 and 0.24 are found to be 16.6 +/- 1.0, 22.1 +/- 1.6 a nd 32.5 +/- 3.2 kcal mol(-1), respectively. The increase of E-a in the mixed system compared to that in the pure (CH2)(6)N-4 implies that in troducing KNO2 impurity in the (CH2)(6)N-4 matrix causes an increase o f the potential barrier of the reorientational motion in (CH2)(6)N-4 l eading to the suppression of the motion. (C) 1998 Elsevier Science Ltd . All rights reserved.