Arrested relaxation, method

The arrested-relaxation method has been applied [227,228] to the reactions of F + H2 and F + D2, and the measured-relaxation technique to F + H2 [229, 230]. These values of / ., and Rv are particularly important since they can be compared with the results of molecular beam and chemical laser experiments (see Table 1.4), and the agreement is satisfactory. The HF vibrational and rotational degrees of freedom absorb approximately 67% and 6% of the total energy and once again there is a marked parallelism between the results for a reaction and its isotopic analog. Preliminary measurements on other reactions producting HF have been reported by Jonathan et al. [230]. 

The experimental vibrational distributions for HBr and HI were taken from ref. 60a, which used the flowing-afterglow method. The rotational distributions were taken from ref. 60b which used the arrested relaxation technique. The vibrational distribution from the latter are shifted slightly to high V levels and increased to 0.63 and 0.65, for HBr and HI, respectively. The vibrational and rotational distributions from HCl were taken from refs. 36 and 59, respectively Tamagake and Setser find = 0.57 and = 0.15. 

A schematic diagram of the measurement is shown in Figure 4.92. An advantage of the enthalpy method is that relaxation of amorphous alloys does not influence the measured specific heat (Cp because the relaxation arises not only during the heating, but also during the thermal arrest. Therefore, relaxation hardly changes C . 

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