Automation of long-path absorption cell measurements

Recent advances have been made in the operation of long-path absorption cells which make them easier to align and improve the accuracy of measurements made with them. Only one person is required now for routine measurements of low absorption coefficients of atmospheric absorbers. Unique gear designs for the adjustment of the cell mirrors are described which utilize low-torque linear drives and make possible rapid changes in pathlength and precision repositioning of the cell output beam at long pathlengths. Automation of cell operation by the use of remote Selsyn controls is described. Several techniques are discussed for precision optical alignment of long-path absorption cells, including the use of infrared radiation sources. The system accuracy which results from these refinements in operation is included.