A Commercial Scanner Applied as a Microdensitometer for Gas Electron-Diffraction Photographic Plates

The present state of the hardware and software of our Joyce-Loebl MK III CS 1970 microdensitometer is reported. The modifications to the existing software necessary for it to be applicable to the data from an Agfa Arcus II commercial scanner are described. The accuracies of the two instruments are compared by the measurement and analysis of photographic plates for two data sets of the short nozzle-to-plate distance of benzene. For about 30000 measured points on both devices, the two instruments give practically the same accuracy, except for very light plates where the Joyce-Loebl results seem to be the best ones. The r_a(C-C) distance obtained from the scanner data is systematically elongated by about 0.5%. Acceptable agreement of the root-mean-square vibrational amplitudes from the two instruments is obtained. A sixfold increase in the number of points applied from the scanner does not improve the agreement very much. The conclusion is that the scanner, in connection with the applied software, can be used as a microdensitometer for gas electron-diffraction plates.