JOURNAL OF MAGNETIC RESONANCE 75, 39-49 (1987) Deuterium NMR on Magneto-A samples of the Chid Smectic C, SE, Phase BAO-GANG Wu AND J. WILLIAM DOANE Depamnent of Physics and Liquid Crystal Institute, Kent State University, Kent, Ohio 44242 Received December 31, 1986; revised March 24, 1987 Unusual deuterium NMR spectml patterns are recorded and analyzed from a magneto- aligned chii smectic C, S$, material. As many as three pairs of singularities can lx observed from a single de&rated site. These patterns are obtaiued when samples witb an aliied pitch axis are oriented at various an&s in the magnetic field. It is shown that values of the tilt angle, 8, and time-averaged quadrupoIe coupling constants Go and asym- metry parameter ? can be obtained with hi@ precision from an angular dependence study of frequencies of singular peaks in the patterns. o 1987 Academic FTEW hc. INTRODUCTION The chiral smectic C, *Sc, phase is an intriguing liquid crystal phase of interest in phase transition studies (I) and with applications in visual displays (2). The fnst mported NMR study of this phase was by Luzar et al. (3) who demonstrated that when a material was cooled from a smectic A, SA, phase into the S?j phase in the presence of a magnetic field the smectic layers, as well as the axis of helical twist, would be aligned by the field, whereas the molecular long axis would tilt away from the field. This feature is opposite from that of the Sc (nonchiral variety) where the molecules align but the layers tilt in the field (4, 5). Such a configuration with tilted layers makes the Sc phase difficult to study with NMR since under reorientation of the sample in the field some of the molecular long axes follow the field to create a diffuse pattern from which it is not possible to obtain precise values of the asymmetry parameter, ii, and tilt angle, 8, necessary to study properties of the phase and transitions into the phase (4, 5). Spinning Sc samples have been used to obtain values of + but again without good precision (6, 7). In this paper we report an angular dependence study of an aligned *S, phase where the imposed helical twist and the layers prevent the molecules from fohowing the direction of the field as the sample is oriented to various angles in the field. Patterns with sharp edge singularities (as many as three pairs for a single deuterated site} allow for measurements of f, 8, and the coupling constant so with a precision suitable to study material properties of the phase. Simulated spectral patterns show the presence of rippled layers in the *Sc phase and are observed when a bulk sample is cooled from the smectic A, SA, into the *S, . The phase diagram of a ternary mixture of compounds is reported which exhibits the chiral nematic, *N-SA-*Sc sequence. 39 0022-2364/87 $3.00 capyti&@ 1987by&achmicRaInc. AUri@sofFepmductioninanyformrescwed.