Each long path cell has either a mounting fixture or a base plate appropriate for the designated spectrometer. These carry two adjustable transfer mirrors to couple the infrared beam to and from the cell. The cell will be placed in the sample compartment in a position that will allow the first transfer mirror to put the focal area of the infrared beam into the entrance aperture of the White cell. On the output side of the White cell the transfer mirror will be able to direct the beam to the detection system.
For the small cells 2.4-PA, 4.8-PA and 7.2-V, each transfer mirror is mounted on a combination of L-shaped components that can be rotated to drive the infrared beam in the two perpendicular directions, X and Y. These cells have mounting slides that fit the standard spectrometer sample holder. All the user needs to do is position the sample holder so that the focal area is midway between the two transfer mirrors.
For the larger cells, the transfer mirrors are on mounts that are aimed in the X and Y directions by two fine-pitch screws. These mirror mounts can also be moved horizontally. The adjustments on the input side are used to put the beam into the cell just off the edge of the field mirror, with the beam being properly collected by the first objective mirror. The figure here shows the assembly of components on the lower end of cell 107-V.
If red laser light is directed along the optical center line in the sample compartment, the red laser spot should be put in the center of the first objective mirror. On the output side of the cell, the transfer mirror movements are used to direct the output beam along the proper path to the detector. After a preliminary alignment with the laser, the infrared signal is observed, and the transfer mirror adjustments are fine tuned to maximize the signal. Transfer mirrors and laser device are shown in the figure. These larger cells will stand vertically in the sample compartment.