ORBITAL RESPONSE TO BACKWARD (E,E') SCATTERING AT LOW AND HIGH-EXCITATION ENERGIES

The response of orbital excitations with K-pi = 1(+) in heavy deformed nuclei to backward (e, e') scattering is studied in RPA on the exampl e of Sm-154. The summed M1 and E2 cross sections are of comparable mag nitude over wide ranges of transferred momenta: 0.9 < q < 1.4 fm(-1) f or low excitation energies E(x) < 9 MeV and 0.6 < q < 1.8 fm(-1) in th e high-energy region 17 < E(x) < 30 MeV. The two responses can be sepa rated at backward angles only for small q, where the M1 response domin ates at low energy and the E2 response in the high-energy region. The transition densities of the single strongest RPA states from the two e nergy regions are similar to that of the scissors state, apart from th eir smaller amplitudes, The spin M1 responses are similar at low and h igh energy and dominant for high q. The orbital M1 response is dominan t up to high q-values at low energy and only for small q at high energ y. The electric response of the low RPA state (mainly C2) is suppresse d at a full backward angle, while it persists at high energy for theta greater than or equal to 165 degrees due to its dominant transverse E 2 component. The E2 strength below 9 MeV and between 13 and 17 MeV bel ongs neither to the isoscalar nor to the isovector giant resonances.