From the measurements of the DS fusion yield with varying US overlayer
thickness (MOD measurements), we have extracted the effective attenuation
interaction length
** L^{eff}_{att}**, which agrees at the 10% level with the
value given by the Monte Carlo using the
elastic cross section
from Ref. [17]:

where the first error is due to the fit and the second due to the uncertainty in the US layer thickness. The attenuation length is determined mainly by the elastic scattering process, thus the agreement between Eqs. 9.1 and 9.2 suggest confirmation of the scattering cross section of Chiccoli [17] at the 10% level. This is the first quantitative measurement of the cross section to our knowledge, as conventional cycling measurements in D/T mixtures are not directly sensitive to this process. We note that dependence of our results on the value of formation rate is rather weak; a change of by a factor of 2 produces variations in

Our data could alternatively be used to extract information on the scattering
angular distribution. A MC calculation assuming isotropic scattering
with the same total cross section as Ref. [17]
resulted in the effective attenuation length:

which is in clear disagreement with our experiment. The elastic cross sections are in fact predicted to have large

In order to reproduce our experimental attenuation length
** L^{eff}_{int}**using the isotropic angular distribution, the total cross section needs to
be half of the predicted value, which seems rather unlikely (the
experimental absolute fusion yield at US thickness zero is reasonably well
reproduced by either model). Thus, our results given in
Table 8.15 confirm the importance of the

Furthermore, the suggestion of the large ** p**-wave contribution
in turn provides indirect yet intriguing experimental evidence for the
existence of the

Finally, our analysis presented here suggests that the measurement by
Strasser *et al.* [195], who assumed an isotropic angular
distribution in the simulation of the
deceleration in deuterium,
may require re-interpretation. Since there is a significant ** p**-wave
contribution also in the
interaction, neglecting its angular
distribution is not justified, as demonstrated in our analysis. Therefore,
their conclusion, which stressed the importance of molecular effects,
should be taken with caution.