B(E2) strength ratio of one- phonon 2+ states of 94Zr from electron scattering at low momentum transfer

Background: The B(E2) transition strength to the 2(2)(+) state in Zr-94 was initially reported to be larger by a factor of 1.63 than the one to the 2(1)(+) state from lifetime measurements with the Doppler-shift attenuation method using the (n, n'gamma) reaction [Elhami et al., Phys. Rev. C 75, 011301(R) (2007)]. This surprising behavior was recently revised in a new measurement by the same group using the same experimental technique leading to a ratio below unity as expected in vibrational nuclei. Purpose: The goal is an independent determination of the ratio of B(E2) strengths for the transitions to the 2(1,2)(+) states of Zr-94 with inelastic electron scattering. Method: The relative population of the 2(1,2)(+) states in the (e, e') reaction was measured at the S-DALINAC in a momentum transfer range q = 0.17- 0.51 fm(-1) and analyzed in plane-wave Born approximation with the method described by Scheikh Obeid et al. [Phys. Rev. C 87, 014337 (2013)]. Results: The extracted B(E2) strength ratio of 0.789(43) between the excitation of the 2(1)(+) and 2(2)(+) states of (94) Zr is consistent with but more precise than the latest (n, n'gamma) experiment. Using the B(E2) transition strength to the first excited state from the literature a value of 3.9( 9) Weisskopf units is deduced for the B( E2; 2(2)(1) -> 0(1)(1)) transition. Conclusions: The electron scattering result independently confirms the latest interpretation of the different (n, n'gamma) results for the transition to the 2(2)(+) state in Zr-94.