Abstract
The preparation of samples for electron spin resonance spectroscopy frequently requires evacuation and sealing of the ESR sample tube to remove oxygen (an efficient radical trap as well as a source of line broadening). This necessitates the manipulation of quartz with the usual difficulties and expense involved (graded seals, etc.). We wish to report that a satisfactory alternative to sealing quartz tubes under vacuum can be constructed using an "O" ring coupling similar to those used to effect glass to metal vacuum connections. As we are unaware of a commercial source of these connectors of appropriate dimensions, we have constructed the system shown here for use with the 4-mm o.d. sample tubes accepted by a Varian E-4 spectrometer. In addition to avoiding the problems of working quartz and being nondestructive of the sample tube, this system leaves the sample susceptible to secondary vacuum manipulations, such as the introduction of controlled quantities of a reactive gas. The material used in the fabrication of the connector is aluminum; however, it seems reasonable that another material, for example, nylon or Teflon, could be used where gas-metal contact must be avoided. Fig 1 illustrates the sample tube.
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