Phase decay

The ratio of the intercepts to indicates that the amplitude or peak value of the a-phase is 2.7 times larger than the one of the P-phase, while the ratio of a to P (or t 2 to tfi2) shows that the a-phase decays at a rate which is 17 times larger than that of the P-phase. 

Gas phase experiments utilized the same laser system but employed a different sample cell, a 1.5 cm long stainless steel cell with CaF2 windows. A turbomolecular pump was used to evacuate the cell down to the vapor pressure of the W(CO)6. The cell was heated slightly to 326 K to increase the vapor pressure and produce an optical density of 1.0. The gas phase decays are not single exponentials, but rather tri-exponentials. This triexponential character will be discussed in the results section. 

Abdel-Alim and Hamielec [18] assume that the radicals do not diffuse between the various phases. Radicals are generated in monomer medium, and here they also decay, either still in solution or already in the solid phased The active centres, generated in the polymer-phase, decay in the same phase their desorption does not occur [17). When the partition coefficient of the initiator between the monomer and polymer-rich phases is equal to unity we can write... 

The available reliable information on the rate coefficient of reaction (xvi) depends almost entirely on fast flow-discharge studies, and, with the exception of one recent shock tube result, direct measurements are confined to near 300 K. Even here there is a factor of two or three disagreement between authors. Results are summarized in Table 39. Uncertainties arise from two major causes. First, the second order gas phase decay of OH is accompanied by a first order heterogeneous decay. Optimization of the separation of the observed decay into its first and second order components is difficult, and this may account for some of the reported discrepancies [222]. Secondly, all the investigations have used the H + NO2 reaction as the source of OH, with the NO2 added downstream of the discharge. The relevant elementary steps causing the growth and decay of OH are then... 

The label migration, observed only in the product from the gas-phase decay, provides the first ecperimental evidence for a degenerate rearrangement of the gaseous phenylium cation. 

This phenomenon of super-radiance is used in the photon-echo technique for high-resolution spectroscopy to measure population and phase decay times, expressed by the longitudinal and transverse relaxation times Ti and T2, see (7.1). This technique is analogous to the spin-echo method in nuclear magnetic resonance (NMR) [904]. Its basic principle may be understood in a simple model, transferred from NMR to the optical region [905]. 

No evidence or apparent reason exists to support the first possibility. Indeed, that channel seems essentially noncompetitive in the gas phase decay from thermal levels, and it is difficult to imagine how an Si Sa internal conversion suddenly could become so efficient. Various authors have proposed that the internal conversion S -So proceeds through an intermediate isomeric state, but this author would prefer to classify this as chemical relaxation,... 

However, a number of metals tend to form carbides, which can be very stable (thermodynamic control) or refractory (kinetic control). In this case, no analyte is released into the vapor phase. Decay of the vapor cloud is influenced by several processes ... 

Field-induced distortions of the blue phases decay rather fast. In the geometry of a Kerr cell (the field is perpendicular to the light wave vector) the field induces the birefringence, 6n, which results in the electrooptical modulation AI of transmitted light. For nearly crossed polarizers... 

Recent progress in the generation of picosecond and sub-picosecond light pulses makes investigations of ultrafast processes occurring during excitation and deactivation of molecular states in solvents possible. The population decay times and the phase decay times of coherently excited molecules can be studied with extremely high time resolution. 

Over the past three years there has been a growing interest in the use of pulse NMR for the analysis of waxes for oil content. This technique relies on the fact that, after a wax has experienced a pulse of radio-frequency radiation, the signals received from the solid and liquid phases decay at different rates and that the amplitude of each signal is proportional to each phase present. The solid signal decays rapidly whereas the liquid signal lasts much longer. The sample is cooled so that the) wax is totally solid and the liquid signal is proportional to the oil content. 

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