A new light producing, dispersing, and collimating system for absorption scanning ultracentrifuges, with special features for computer-controlled data collection using a stepping motor

This paper describes in detail a simple, light producing and handling system which differs greatly from the commercial unit presently used by most investigators, and which overcomes a number of its disadvantages. The apparatus is designed so that it can easily be substituted for the light producing, dispersing, and collimating section of the commercial photoelectric scanners, with no further changes in the commercial scanners except the substitution of optical flats for the collimating and condensing lenses in the bottom and top, respectively, of the rotor chamber. The most outstanding feature of this new system is that the use of a faster monochromator ( f 75.3 ) and a cylindrical lens theoretically increases light intensity by up to 100 times that of the commercial scanner, under otherwise identical conditions. Other advantages include the following: (1) For collecting and collimating light, two pairs of mirrors give a precell optical system focused in the radial direction at all wavelengths of light; (2) these components and the lamp are located on a table outside the centrifuge, so virtually any size of lamp can be used; (3) the entire precell optical system is a self-contained unit which, within reasonable limits, may be moved to any desired location without markedly affecting the quality of the collimated light; and (4) the optical path length has been shortened, providing less dissipation of light energy. The principles behind the selection and design of the key components are discussed. New alignment procedures and apparatus developed to aid in fast, easy, accurate alignment are described and discussed. Several components for use with a system using a computer-controlled stepping motor scanner for collection of data are also described. This system is simple enough and is documented in sufficient detail so that other interested workers, even those with little or no optics experience, can duplicate and use the system.