SAMPLE CELL FOR HIGH-PRECISION TEMPERATURE-DEPENDENCE NMR EXPERIMENTS

A simple sample temperature control system is described which minimizes temperature gradients and provides for accurate and precise control of sample temperature. The sample is confined in a standard 5 mm o.d. NMR tube, supported in a standard 10 mm o.d. tube, through which a fluid, whose temperature is regulated in an external thermostat, is rapidly circulated by way of a double-pass liquid-flow arrangement. The device can be readily used in any standard 10 mm NMR probe. When water is used as the cryogenic fluid, sample temperatures in the range 273 to 370 K, with an accuracy, precision, and resolution (settability) of ±0.005 K, are accessable. We have extensively used the system to study phase transitions and phase behavior of liquid crystals, although many other applications may be envisaged. Herein, the performance characteristics of the device are demonstrated by 2H and 133Cs experiments on the cesium pentadecafluorooctanoate (CsPFO)/water liquid-crystal system. © 1992.