Nuclear Reaction Rates in a Plasma: The Effect of Highly Damped Modes

The fluctuation-dissipation theorem is used to evaluate the screening factor of nuclear reactions due to the electromagnetic fluctuations in a plasma. We show that the commonly used Saltpeter factor is obtained if only fluctuations near the plasma eigenfrequency are assumed to be important (\omega \sim \omega_{pe}\ll T (\hbar=k_{B}=1)). By taking into account all the fluctuations, the highly damped ones, with \omega >\omega_{pe}, as well as those with \omega\leq\omega_{pe}, we find that nuclear reaction rates are higher than those obtained using the Saltpeter factor, for many interesting plasmas.