Picosecond Spectroscopy of Transient Absorption in Pure KCl
We present a brief review of various metastable and stable absorbing species generated during electron-hole recombination in alkali halides, emphasizing transient components which are the dominant features on the time scale of short laser pulses. The F-band in KC1 falls in this category, since it is produced with high efficiency (∼ 15% of e-h recombinations) but decays to 10% of its initial value (τ ≲ 20 μsec) even at liquid helium temperature. We report experiments in which a single 20 psec pulse of 2660 Å light produces dense coloration in a pure KC1 crystal at flux levels too low to cause damage from other processes such as avalanche breakdown. We have used delayed pulses of 5320 Å light to monitor the rise of the absorption on a picosecond time scale, as well as its decay (at room temperature) on a nanosecond time scale.
KeywordsProbe Pulse Transient Absorption Alkali Halide Transient Defect Intense Laser Pulse
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