Physics Letter~ B 319 (1993) 29-'a4 Norlh-Holland PHYSICS LETTERS B Dynamics of Coulomb dissociation in relativistic mean field theory D. Vretenar. Physws Department. l-~Tc,,Ity of .~wnce. ~'m verstt.v of Zagreb. 41000 Zagreb. ('roatta H. Berghammer I and P. Ring l)hvslk Department der 7"echmschen L'mversJtdt Munchen. D-85 "48 (;archmg. F RG Rocelved 26 July 1993. revised manuscript received I I October 1993 Echtor: C. Mahaux Time-dependent relatKistlc mean field theoD' is used to dcscr)be the d)namlcs of Coulomb excttahons of nuclei. As an example ~,e consider the nucleus t~'O. At small modem energies of the proJectile we observe tsovector d~pole oscillations that correspond to the grant dtpole resonance. With increasing excitatmn energy, the motion Ix'comes mcreasmgl!, anharmomc, and finally a full dtssociatton of toO into proton and neutron clusters is observed. Coulomb excitations by relativistic heav~ ions pro- vide a well-defined excitation mechanism that allows a detailed study of the response of nuclei to the action of a strong, extremly short Lorent?-contracted electro- magnetic pulse [ I ]. This type of reaction has recently gained considerable theorehcal and expcnmental in- terest with the first observations of double excitation ofthe giant dipole resonance [ 2.3 J. With higher imtial energy multiple excitations are possible and. finally. a full Coulomb dissociation should be observed [4]. In refs. [5] and [6] we have used a time depen- dent verston of the relativistic mean field Walecka model to investigate the dynamics of Coulomb exci- tations of a one-dimensional slab of s.~mmetric nu- clear matter extending homogeneously to infinit) in the perpendicular plane. Time-dependent versions of the Walecka model have been used m the descrip- tion of relattv~stic heavy-ion collismns [7.8]. In the present article we apply the model to the investiga- tion of the dynamics of Coulomb excitations for the realistic three-dimensional case, and. in particular, to the description of Coulomb dissociation of 160. The dynamics of Coulomb excltahons is described m the hme-dependent relativistic mean field Walecka Supported by the Bundesmmlstermm fur Forschung und Technologic under the projt, t 06 TM 733 model [9-12]. The model Lagrangian density is [13] C = ~ (i;..O - m)q/ + ~(Oa)" - U(a) 1() Ou" I " " 4 --,v-~ + ~/'Ph't,(O" _ L.~. ~..u, .. g,,v/a~/- g,o~/;'.~o~/- gp~)', pr~u 4" lavl -e~;'-..! (I ,r~._ ....... _~) ,. (I) The nucleons (~) are described as Dirac spinors in- teracting by the exchange of several mesons: isosealar scalar o-meson, tsoscalar vector oa,-meson and isovec- tor vector p-meson, m is the mass of the nucleon, nto. m,j. and mp are the masses of the e-meson, the co- meson, and the p-meson, and the corresponding cou- pling constants g,. go. and gp for the mesons to the nuclcon, e:/4n = I / 137. For the sigma meson we use the nonlinear potential [14] • I 4 U(o) = !,n~a" + ]g,aJ + ~gw • (2) The field tensors for the vector mesons and electro- magnetic field are Qu ; = i)u ~O," _ i),'O)u , (3) 0370-2693/93/$06.00 @ 1993-Elsc,.ler ~)¢nce Pubhshers B.V. 411 rights reserved 29 ~,1)10370-2~93('031[.I 390-I