Abstract: A method of forming a pair of identical spherical mirrors having their centers of curvature separated in space. A blank having substantially parallel planar front and rear surfaces is provided. The front surface is scored to divide it into two surface segments. The entire front surface is then ground to a spherical shape. The blank is then bent along the scored region to separate in space the centers of curvatures of each of the surface segments.The foregoing abstract is not to be taken either as a complete exposition or as a limitation of the present invention. In order to understand the full nature and extent of the technical disclosure of this application, reference must be had to the following detailed description and the accompanying drawings as well as to the claims.

Abstract: An improvement in the method of assembling a pair of windows and a spacer by amalgamation to form a sampling cell. The improvement comprises evaporatively depositing a thin layer of metal on each of the windows prior to amalgamating them with the spacer.