ELECTRON SCREENING IN MOLECULAR FUSION REACTIONS

Recent laboratory experiments have measured fusion cross sections at c enter-of-mass energies low enough for the effects of atomic and molecu lar electrons to be important. To extract the cross section for bare n uclei from these data (as required for astrophysical applications), it is necessary to understand these screening effects. We study electron screening effects in the low-energy collisions of Z = 1 nuclei with h ydrogen molecules. Our model is based on a dynamical evolution of the electron wave functions within the TDHF scheme, while the motion of th e nuclei is treated classically. We find that at the currently accessi ble energies the screening effects depend strongly on the molecular or ientation. The screening is found to be larger for molecular targets t han for atomic targets, due to the reflection symmetry in the latter. The results agree fairly well with data measured for deuteron collisio ns on molecular deuterium and tritium targets.