POLARIZATION MEASUREMENTS FOR ATOMIC AND MOLECULAR-EMISSIONS IN THE VACUUM-ULTRAVIOLET

The various factors involved in making measurements of the polarizatio n of weak atomic and molecular emissions in the vacuum ultraviolet are discussed. Materials in current use are evaluated with particular emp hasis on the most important sources of systematic error. For measureme nts of circular polarization these involve possible misalignment of th e retarder as well as uncertainty in the phase shift itself. The circu lar polarization of Lyman alpha is considered as a particular example. For measurements of the linear polarization fraction, the need for se lection of devices with high polarizance is stressed, together with ca re in choice of materials and operating environment to minimize the ri sk of temporal drift of device characteristics. Errors relating to the actual detection process of very weak optical signals are also consid ered.