Microwave T-jump

To determine kinetic and thermodynamic parameters involved in these equilibria by direct relaxation measurements, very sensitive and rapid T-jump apparatuses appeared to be necessary. This objective can be attained by a fast Raman laser T-jump (time resolution about 10 s) and by a repetitive microwave T-jump (sensitivity better than 10 optical density units). 

Fig. 3. Microwave T-jump relaxation of cytosine as a function of the number, n, of accumulations repetition rate 20 Hz. Experimental conditions X = 300 nm tf = 23°C pH 6.4 ...

T-Jumps can also be produced by microwave heating and by laser pulse absorption. These methods remove the restriction to low-resistance solvents any solvent capable of absorbing energy of the applied frequency may be used. The heating time can be extremely short with laser heating. ... 

The magnitude of the temperature change required for a T-jump depends on the enthalpy of the reaction, but 5 °C is typical. This implies an energy deposition of about 20 J cm , which could be supplied by a beam of radiation, such as microwaves or visible light. A high-pressure laser T-jump apparatus has been reported. ... 

A summary of the results to date pertaining to lipid phase transition kinetics established by TRXRD is presented in Table 1. Included in the table are data obtained using synchrotron X-radiation and a sampling of data collected using conventional X-ray sources. Entries are arranged by the type of trigger used to effect the transition, which includes temperature, pressure and composition. The means by which T-jumps were implemented include fluid flow (air or liquid) around the sample or sample compartment, as well as Peltier, Joule (capacitance) and microwave heating. 

The analysis of the dynamics of very fast processes is however only one of the aspects in relaxation measurements. Another aspect is the problem of the detection of chemical or biological equilibria even when they are very one-sided. So we have developed a very sensitive T-jump apparatus using repetitive heating generated by a 250 kW microwave source. ... 

In the temperature-jump ( T-jump ) and the pressure-jump ( P-jump ) methods a gaseous or liquid system is subjected to a rapid heating or a rapid change in pressure. Aheating pulse can be delivered by a burst of microwave radiation or by the passage of a brief pulse of electric current if the system is electrically conductive. A rapid change... 

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