Charge-transfer-device detectors have become common in many systems used for chemical analysis, and are often an attractive alternative to photomultiplier tubes, photodiode arrays, and vidicons. Charge-transfer devices are solid-state, array detectors sensitive to photons from the far-infrared to the x-ray region of the spectrum. Today, most commercially available instruments use silicon-based detector technology, which has optimum sensitivity from the near-infrared to the x-ray region. Some important characteristics of properly operated scientific-grade charge-transfer devices are high sensitivity, large dynamic range, remarkably low dark current, very low read noise, and multichannel capability.