Automation of a Wide-range, General-purpose Spectrophotometric System

The application of an IBM 1800 computer to the control and data acquisition functions of a wide-range spectrophotometric system is described. The optical part of the system is designed primarily for solid-state spectroscopy in the reflectance mode, the energy range of interest being roughly 1 to 12 eV (10
⁴
to 10
⁵
cm
⁻¹
). The operations of the computer include regulation of the wavelength setting, determination of the system gain, analog-to-digital conversion of the output signal, and positioning of the sample and detector. Two experimental configurations are employed, depending on whether or not the sample and detector are to remain stationary or to be repositioned during a run. The former holds for electroreflectance, fluorescence, and photoconductivity studies, while the latter pertains to ordinary reflectance and transmittance measurements. The principal advantage to be derived from on-line computer control of such experiments, besides more rapid accumulation and reduction of data, is the improvement in signal-to-noise ratio by averaging many repetitive scans over the same energy range. The emphasis in this paper is on the software used to implement these operations.