Time resolved measurement of the 1.4 micron absorption band in water during the shock-induced liquid to ice-VII phase transition

Reverberation compression of a thin water layer, sandwiched between sapphire windows under plate impact, transitions the water from a liquid to a supercooled liquid to solid ice vii. We measured the transmission spectrum of the 1.4 micron absorption band during this transformation using a spectrum to time mapping technique which consists of a train of supercontinuum laser pulses sent through a dispersive spool of optical fiber, a photo detector and a digital oscilloscope. The fiber fed and chirped laser pulses are double passed through the water cell which is compressed with the impactor of a light gas gun and recorded on the oscilloscope. The spectrum changes only slightly during compression to a supercooled liquid, it then more substantially red shifts and narrows as ice vii forms. The dynamic spectrum is compared with prior diamond anvil cell data.