Heat capacities, spurious

Let us examine the data of the third measurement on the metallized wafer. There are two contributions to the heat capacity, a linear contribution and a spurious one. The spurious contribution may be interpreted as the high temperature side of a Schottky anomaly. In this hypothesis, the heat capacity per unit volume of the metallized wafer may be... 

Up to now, in the formulation of a bolometer model, only the heat capacity of itinerant carriers was considered [57], However, our measurements show that, even at 24 mK, the presence of a spurious heat capacity in the thermometer increases the expected value of the pulse rise time. We expect that the spurious contribution in Fig. 12.17 increases down to the temperature of the Schottky peak at T = k.E/khT about 10 mK. Since gc decreases at low temperatures, the total effect on pulse rise time and pulse amplitude can be dramatic at lowest temperatures. In reality, the measured rise time of CUORICINO pulses is about three times longer than that obtained from a model which neglects the spurious heat capacity of the thermistor. For the same reason, also the pulse amplitude is by a factor two smaller than the expected value (see Section 15.3.2). 

Heat capacities of activation have been determined for relatively few other reactions, probably because the necessary experimental accuracy is more easily reached in solvolytic studies. Unfortunately, some of the values reported in the literature cannot be accepted either because they are obviously spurious or because separate sets of workers studying the same or similar reactions obtained quite different results. Examples of investigations which appear to be free from such objections are given below but it must be pointed out that the findings are often surprising and that mechanistic conclusions cannot always be drawn from the information available so far. 

As we shall see, most authors ascribe this effect to the energies of the initial state and the transition state being influenced by temperature to different extents. In this interpretation, therefore, these reactions exhibit a temperature-dependence of Ea that corresponds to the fundamental definition of a specific heat of activation, given in Section III. A (100). This is in contrast with the nonzero values of dEaldT derived in the previous section. Robertson et al. (142,149) have gone so far as to call them spurious heat capacities, whereas the effects we are dealing with in this section are termed real heat capacities. 

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