Large-basis space and mesonic effects on the 7Li form factors

Abstract The electron-scattering form factors of 7 Li are investigated in the nuclear shell model. Calculations have been performed in the Op-shell-model space as well as in the complete (0 + 2)ħ;ω model space. Meson-exchange-current corrections to the transverse form factors are included. Only in the extended model space we find good agreement with experiment for all calculated form factors up to momentum transfer 3 fm −1 . Meson exchange currents enhance the transverse form factors at large momentum transfer, bringing theory considerably closer to experiment. For the transition to the J π = 7 2 − second excited state ( E x = 4.63MeV) we find that the high multipoles E4 and M5, which dominate the transverse form factor at momentum transfer q >3fm −1 , are mainly induced by meson exchange currents and not by the nuclear structure involved. A comparison of the transverse form factor of the J π = 7 2 −1 state to the one of the J π = 1 2 − first excited state ( E x = 0.478 MeV) seems to give experimental confirmation of this finding.