Acoustic transit

Time resolution of the enthalpy changes is often possible and depends on a number of experimental parameters, such as the characteristics of the transducer (oscillation frequency and relaxation time) and the acoustic transit time of the system, za, which can be defined by ra = r0/ua where r0 is the radius of the irradiated sample, and va is the speed of sound in the liquid. The observed voltage response of the transducer, V (t) is given by the convolution of the time-dependent heat source, H (t) and the instrument response function,... 

Figure 17. Semilogarithmic plot of the heat (1 — a) stored by Pr and by the ground and excited-state r700s versus the effective acoustic transit time at two excitation wavelengths Aejc = 660 nm ( — ) and 695 nm (O—O). Data corrections for the...

Acoustic transit time The acoustic wave time decreases relative to either water or free gas however, the acoustic transit time for hydrates is like ice-bearing sediments. See Section 7.4.2 for BSR and AVO in ocean applications... 

The temporal response of the thermal lensing technique is limited by the acoustic transit time the heated liquid must expand in volume for the lens to be formed and this depends in particular on the size of the heated region. In practice the observation time scale is of about 1 ps to a few ms. 

Compared to the studies using the population grating (Section II.C), studies on the excited-state dynamics from the heating effect have been rather limited. A probable reason is that the time resolution of the signal is determined not only by the pulse width but also by the acoustic transit time, Tac = A/v, as described in Section II.B.l. 

The pressure geireration (fcscribed by Eqs. (27) and (28) in solution is finally to be detected by a piezoelectric transducer. Since the detector is not din tly introduced into solution in our expmments [18, 24], the sound wave must be conducted by difierent connecting materials to the piezoelectric detector and thus passes throuj various phase boundaries. The acoustic transition coefficient represents a measure for the crossing of the acoustic wave at these boundary surfaces [%, 97]. For the crossover of the sound wave from medium 1 into medium 2 we have ... 

Figure 2 Timescales for the radiative emission and relaxation processes. The shaded area indicates the typical response time of a PA resonator equipped with a microphone. The thick line represents the acoustic transit time. The wavy lines depict the radiative emission and the horizontal lines the range of relaxation processes characterized by the relaxation time r.

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