127I Pure Quadrupole Resonance Spectrum of Orthoperiodic acid, H5IO(

The NQR-spectrum of 127I in orthoperiodic acid, H 5 I0 6 , has been studied on powder samples in the temperature range 77 K T 398 K. The resonance frequencies vx of the transition i n ( ± 3 / 2 ) ^ m ( ± l / 2 ) are 45.248 + 0.005 MHz (77 K) and 4 4 . 9 7 6 ± 0 . 0 0 5 MHz (296 K ) . For the transition TO(±5/2) ^ I t o ( ± 3 / 2 ) the resonance frequencies v2 are 8 3 . 4 7 8 ± 0 . 0 0 5 MHz (77 K) and 83.960 ± 0 . 0 0 5 MHz (296 K) . The corresponding quadrupole coupling constants, e2qQ/h, are 282.977 ± 0 . 0 0 5 MHz (296 K) , and 281.892 ± 0.005 MHz (77 K ) . The asymmetry parameters rj have been determined as 0.2372 ± 0 . 0 0 0 1 (296 K) , and 0.2580 ± 0 . 0 0 0 1 (77 K) . A small change of 0.4% for e2 q Q/h is accompanied by a rather large change of 21% for rj within the temperature range investigated, e2 q Q/h=f (T) shows a maximum at ~ 313 K. No evidence of phase transition has been observed by NQR spectroscopy between 77 K and 398 K.