Hyperquenching

A rather different type of advanced EPR concerns the detection of transient intermediates, which was briefly discussed in Chapter 13, Section 13.4. Here, the advanced (i.e., instrumentally complex and with its own price tag) refers to the sample preparation, not to the spectroscopy. The common denominator of the rapidfreezing (> 5 ms) or even hyperquenching ( 1 ms) kinetic equipment with double resonance and high frequency EPR is the requirement for a specialized laboratory and knowledge infrastructure. This makes detailed planning of experiments, including expert consultancy, equally important. 

Cherepanov, A.V. and DeVries, S. 2004. Microsecond freeze-hyperquenching development of a new ultrafast micro-mixing and sampling technology and application to enzyme catalysis. Biochimica et Biophysica Acta 1656 1-31. 

Microsecond Freeze-HyperQuench. RFQ, Rapid Freeze-Quench. 

G. P. Johari, A. Hallbriicker and E. Mayer, The glass-liquid transition of hyperquenched water. Nature, 1987, 330, 552-553. 

V. Velikov, S. Borick and C.A. Angell, The glass transition of water, based on hyperquenching experiments. Science, 2001, 294, 2335-2338. 

There exist different types of ice (see also Fig. 1.12). The ice we know from everyday live (also snow) has a hexagonal structure. At higher temperatures and pressures ice can also form a cubic structure 4). Other forms of ice are called II, III, V, VI, VII, VIII, IX and X. The difference between these forms is their crystalline structure. One also speaks of low-density amorphous ice (LDA), high-density amorphous ice (HDA), very high-density amorphous ice (VHDA) and hyperquenched glassy water (HGW). 

LDA forms by extremely quick cooling of liquid water ( hyperquenched glassy water , HGW), by depositing water vapour on very cold substrates ( amorphous solid water , ASW) or by heating high density forms of ice at ambient pressure ( LDA ). 

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