Performance of the 6VOPE high resolution VUV spectroscopic facility in the photoelectric detection mode.

Absorption measurements of krypton gas have been carried out to evaluate the performance of the high resolution spectroscopic facility 6VOPE using photoelectric detection. The 6VOPE is designed to make use of high spectral orders and consists of a 6.65-m vertical dispersion off-plane Eagle spectrograph/monochromator and a zero-dispersion tandem grating predisperser system. Focal plane scanning is used to achieve high resolving power (>==10(5)) for photoelectric measurements in the 40-200-nm range. A description is given of the mechanism and performance of the 6VOPE in the focal plane scanning mode. The resolving power and focused stray light level at ~88 nm are estimated experimentally to be greater, similar1.5 x 10(5) and less, similar 3%, respectively. Contrary to the usual experience the focused stray light of the 6VOPE is composed entirely of VUV light scattered from the main grating.