X-RAY STUDIES OF BOND-ORIENTATIONAL ORDER IN LIQUID-CRYSTALLINE ORTHOGONAL HEXATIC-B PHASE

X-ray scattering measurements have been carried out for free-standing, thick . monodomain films of the orthogonal hexatic-B phase. From Four ier analysis of X-scans, 6n-fold-symmetry order parameters were determ ined and proved to fulfill the scaling relation C6n = C6n+lambdan(n-1) . The temperature behavior of C6 and lambda was found nonuniversal whe n comparing homologues, PIR5 and PIR7, differing in their range of the hexatic phase. The hexatic order parameter varies with the critical e xponents 0.25, 0.20 (+/- 0.03), respectively. For comparison results f or compound RFL6, of other homologue series, are presented.