Time-resolution techniques have been used to observe self-reversal of iron lines as a function of time. The spectrum of iron was excited with an electronically regulated ac arc source controlled to a high precision in time at currents up to 200 A. Time resolution was achieved with the aid of a disk, having an Archimedes spiral slot, rotating in front of the slit of a 2-m Ebert spectrograph. In the present spectral region, two types of self-reversed iron lines could be easily distinguished for transitions terminating on levels above the ground state. For lines terminating on the a5F levels, the width of the self-absorbed core is greatest at the end of the discharge. For lines terminating on levels above a5F, the self-reversed core either disappears or becomes very narrow at the end of the discharge.
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