[en] Design and installation of a high resolution energy-loss electron scattering system at the Darmstadt linear accelerator are described. The apparatus consists of a beam transport system with two 70⁰-dipole bending magnets, eleven quadrupole focussing magnets, a five quadrupole magnet set as a rotating element, and a magic angle (169.7⁰) spectrometer for analyzing the scattered electrons. For a primary momentum spread Δp/p₀ = 3 x 10^-3, a spectrometer acceptance solid angle Ω = 5 msr, and a 10 mg/cm² thick Be target, the resolution was measured to be delta p/p₀ = 4 x 10^-4, equivalent to 25 keV for 60 MeV electrons. (orig.)

[en] The excitation of the J^π;T=1⁺;0 and 1⁺;1 states at E_x=12.71 and 15.11 MeV in ¹²C has been studied at momentum transfers q<0.5 fm^-1 in inelastic electron scattering. The corresponding ground state radiation widths and transition radii for the isoscalar and isovector transition are deduced as Γ_γ0=0.32(2) eV, R_tr=2.95(9) fm and Γ_γ0=35.9(6) eV, R_tr=2.63(4) fm, respectively. For the evaluation of Γ_γ0 and R_tr for the transition to the 15.11 state (e,e'), data of the present work have been combined with older data from other low energy electron accelerators. The results support the strong isospin mixing of the two 1⁺ states, and in the frame of a two-state model a Coulomb matrix element < H_C>=118(8) keV is derived. This value agrees with other experiments using electromagnetic or pionic probes but is much more accurate. Furthermore, the measured difference in the transition radii for the isoscalar and isovector transitions allows for the first time a unique determination of the sign of < H_C>

[en] The isospin-forbidden electroexcitation of the 1^-, T = 0 state at 7.12 MeV in ¹⁶O has been studied for momentum transfers q = 0.22 - 0.49 fm^-1. The form factor at these momentum transfers is determined by the sum of the isospin T = 0 part and a T = 1 contribution. A single particle-hole harmonic oscillator shell model calculation reproduces the q-dependence of the measured form factor which shows that the isovector contribution interferes destructively with the isoscalar part and has a strength of about 2% of the T = 0 amplitude. (orig.)

[en] Improvements of the Darmstadt electron linear accelerator prerequisite to the installation of a high-resolution energyloss system are described. These are a 200 kV, 5 mA grid-controlled DC injector and an RF klystron driver consisting of a quartzstabilized oscillator, a PIN-modulator, and a 1 kW driver klystron. The installation of a new vacuum system and necessary rearrangements of the shielding are outlined. (orig.)

[en] The Al-27(e, e-prime) reaction measured at low momentum transfers had been used to determine the ground-state radiative transition strengths from levels in the excitation region between 6 and 8 MeV. The transition strengths can be directly correlated with the corresponding transitions in the mirror nucleus Si-27, where they are of relevance for the depletion of Al-26 by radiative proton capture into Si-27. The majority of the observed transitions are M1 transitions, which would require d-wave low-energy proton capture on Al-26. 14 references

[en] Design and installation of a high resolution energy-loss electron scattering system at the Darmstadt linear accelerator are described. The apparatus consists of a beam transport system with two 70⁰-dipole bending magnets, eleven quadrupole focussing magnets, a five quadrupole magnet set as rotating element, and a magic angle (169.7⁰) spectrometer for analyzing the scattering electrons. For a primary momentum spread Δp/p₀ = 3 X 10^-3, a spectrometer acceptance solid angle Ω = 5 msr, and a 10 mg/cm² thick Be target, the resolution was measured to be Δp/p₀ = 4 X 10^-4, equivalent to 25 keV for 60 MeV electrons. (Auth.)

[en] The electroexcitation of the 2⁺, T=1 state at 16.11 MeV in ¹²C has been investigated for momentum transfers q<0.5 fm^-1. Longitudinal and transverse contributions were separated by means of the angular dependence of the cross section. The ground-state radiative width has been determined to GAMMAsub(γ)⁰ = 0.346 +- 0.041 eV and the contribution of the magnetization density to the current has been derived from the q-dependence of the reduced transition probability. These quantities are compared to 1p-1h shell-model and intermediate coupling model calculations which are both in disagreement with the experimental numbers. This discrepancy is however, partly removed when collective states with 2 (h/2π)ω excitations are included. (Auth.)

No abstract available

[en] The isospin-forbidden electroexcitation of the 1^-, T=0 state at 7.12 MeV in ¹⁶O has been studied for momentum transfers q=0.22-0.49fm^-1. The form factor at these momentum transfers is determined by the sum of the isospin T=O part and a T=1 contribution. A single particle-hole harmonic oscillator shell model calculation reproduces the q-dependence of the measured form factor which shows that the isovector contribution interferes destructively with the isoscalar part and has a strength of about 2% of the T=O amplitude. (Auth.)

[en] High-resolution inelastic electron scattering (FWHM approximately equal to 33 keV) with 50 MeV and 63.5 MeV electrons on ²⁰⁸Pb has been used to study magnetic excitations between Esub(x) = 6 MeV and 8 MeV. Angular distributions were analyzed in terms of the DWBA with RPA wave functions. Eight Isup(π) = 2- states carrying a total strength ΣB(M2) = 8500 μ²sub(K) fm² have been found. The strong fragmentation is in qualitative agreement with theoretical predictions. (orig.)