Desorption mechanism time dependence

Fig. 9. Incidence energy dependence of the vibrational state population distribution resulting when NO(u = 12) is scattered from LiF(OOl) at a surface temperature of (a) 480 K, and (b) 290 K. Relaxation of large amplitude vibrational motion to phonons is weak compared to what is possible on metals. Increased relaxation at the lowest incidence energies and surface temperatures are indicators of a trapping/desorption mechanism for vibrational energy transfer. Angular and rotational population distributions support this conclusion. Estimations of the residence times suggest that coupling to phonons is significant when residence times are only as long as ps. (See Ref. 58.)...

Much like thermal blankets, thermal well systems do not require costly excavation and they also offer additional benefits. They have been used to treat contaminants at depths up to 5.5m below the surface and much of the contaminants are destroyed in situ through oxidation or pyrolysis reactions.Furthermore, thermal well systems offer uniform heating and consequent treatment of contaminants is effective across a wide range of soil types. The long residence time favors desorption mechanisms that may be time dependent. ... 

The properties of polycarbonate beside its molar mass distribution (D=Mw/Mn) depend often of type and amount of end groups, cycles, additives and branch. In particular the end chains constitute the fingerprints of its polymerization procedure, of its thermal and mechanical history and of their environmental use. Several tools such as NMR, FT-IR and Mass Spectrometry were used to determine these peculiar characteristics of PC. In particular the matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) has successfully been applied to obtain these information (49,50). MALDI-TOF technique is able to look each molecule even in a complex mixture (51-53), to obtain information on the end groups and structure (linear, cyclic or branched) of the macromlecular chains as a function of the synthesis and processing conditions. 

The view that BdR is at best the adsorption-desorption balance of rubber segments on CB sites at a given time (and temperature) is clearly supported by the above model. As long as an equilibrium is not reached however, the adsorption-desorption mechanism evolves while the compound is at rest, hence the observed variations upon storage. How fast this equilibrium BdR is reached depends on the chemical nature of the rubber, on the compound formulation, on the mixing and the dump compound storage conditions. 

The time dependent changes in the stress-strain data of uniaxial static simple tension were monitored both for classical PU systems and for novel dybenzil PU and were followed in dependence of PU thickness. 300% tensile stress (ct °°) was proved to be a valuable criterion to follow the mechanical properties evolution for PU of different thickness. The evolution of mechanical properties in time, was assessed in conjunction with the kinetics of other processes, e.g. kinetics of free isocyanic (NCO) groups consumption, kinetics of H2O absorption and desorption and with the desorption kinetics of CO2 resulted during the formation of urea group. It concluded that the CO2 desorption appears to be the slowest dynamic process (Fig.2) and its rate influences the rate of PU postcuring process. 

The temperature dependence of S0 measured at normal incidence and Ex = 0.39 eY is reported in Fig. 11 for Ag(2 10) ( ) and compared with the behaviour observed at the same E and 0 for Ag(l 0 0) (dashes) and Ag(l 1 0) (solid line) at the same E and 0. The data for Ag(41 0) are reported, too ( , O, x) for two different 0, corresponding to similar values of S0. We notice that all surfaces show a smooth T dependence except for Ag(l 0 0), for which S0 drops abruptly beyond T = 170 K [100], i.e. as soon as desorption from the molecular well becomes important over the time scale of the experiment (0.3 sec). The Ag(4 1 0) and Ag(l 1 0) curves have the same behaviour up to 350 K, at which temperature S0(T) becomes steeper for Ag(41 0). Such difference is due to the dissociation process, which occurs only at steps for Ag(41 0) and takes place at regular sites for Ag(l 1 0). When the lifetime in the chemisorbed precursor becomes shorter than the time needed to search for the defect, the dissociation probability for Ag(41 0) decreases more rapidly with respect to a situation where no searching for an active site is necessary. The S0(T) curve of Ag(2 10), on the other hand, nearly perfectly overlaps with the one of Ag(l 1 0). The decrease of S0(T) on Ag(2 1 0) tells us further that the dissociation mechanism is mediated also in this case by a short lived molecular precursor, which has the choice between desorbing and dissociating. 

---