S. N. Choudry

Erratum: 2 1 + → 0 1 + transition strengths in Sn nuclei [Phys. Rev. C 76 , 021302(R) (2007)]

In our previous work [1], we presented a new lifetime measurement for the 21 state in 112Sn, as determined through the Doppler-shift attenuation method following the (n, n′γ ) reaction [2]. Here, the theoretical F (τ ) value with which one compares the measured F (τ )exp should be modified by an additional term to correct for the recoil velocity distribution when scattering at a neutron energy, En, well above the energy threshold, Elevel [2]. For an angular distribution approximately isotropic in the center of mass, the total F (τ ) is given by

Low‐lying Collective States in 136Ba

Low‐lying collective states in 136Ba were investigated with (n,n′γ) techniques, including Doppler‐shift attenuation lifetime measurements. The level spins, lifetimes, branching ratios, multipole‐mixing ratios and transition strengths reveal candidates for symmetric‐phonon states up to third order. The 2ms+ mixed‐symmetry state was confirmed as unfragmented and a candidate for a [21+⊗2ms+]3+ two‐phonon mixed‐symmetry state is proposed.

Multiphonon states in {sub 56}{sup 136}Ba{sub 80}

Low-lying multiphonon states in {sup 136}Ba have been populated with the inelastic neutron scattering reaction. Excitation functions were performed at neutron energies from 2.2 to 3.9 MeV, and {gamma}-ray angular distributions were measured at 2.5, 3.0, and 3.5 MeV. Lifetimes have been determined using the Doppler-shift attenuation method, and electromagnetic transition rates have been deduced. The previously assigned 2{sub 1,ms}{sup +} mixed-symmetry state at 2128.9 keV has been confirmed and is not greatly fragmented. For the first time in the N=80 isotones, a 3{sub 2,ms}{sup +} two-phonon mixed-symmetry state is proposed. In addition, the 2{sub 5}{sup +} and the 4{sub 3}{sup +} levels at 2222.7 and 2356.4 keV, respectively, decay with large B(M1) values to the two-phonon 2{sub 2}{sup +} and 4{sub 1}{sup +} states, respectively, which suggests two-phonon mixed-symmetric character. Their excitation energies, however, are not consistent with this interpretation.Low-lying multiphonon states in 136 Ba have been populated with the inelastic neutron scattering reaction. Excitation functions were performed at neutron energies from 2.2 to 3.9 MeV, and γ-ray angular distributions were measured at 2.5, 3.0, and 3.5 MeV. Lifetimes have been determined using the Doppler-shift attenuation method, and electromagnetic transition rates have been deduced. The previously assigned 2 + 1,ms mixed-symmetry state at 2128.9 keV has been confirmed and is not greatly fragmented. For the first time in the N = 80 isotones, a 3 + 2,ms two-phonon mixed-symmetry state is proposed. In addition, the 2 + 5 and the 4 + 3 levels at 2222.7 and 2356.4 keV, respectively, decay with large B(Ml) values to the two-phonon 2 + 2 and 4 + 1 states, respectively, which suggests two-phonon mixed-symmetric character. Their excitation energies, however, are not consistent with this interpretation.

Search for Multiphonon and Mixed‐Symmetry States in 127I

The low‐spin structure of 127I has been studied using the (n,n′γ) reaction at neutron energies ranging from 1.2 to 2.3 MeV and the (n,n′γγ) reaction at 3 MeV. New excited levels and γ‐rays have been identified by using excitation functions and coincidence data. Lifetimes were also determined from an angular distribution experiment. Future work involves determining multipolarities and spin assignments in order to obtain B(M1) and B(E2) values.

Symmetry and structure tests in 18O and 18Ne

Isospin (T) symmetry assumes charge symmetry and charge independence are explicit in nuclear structure. Whereas charge independence implies the nn, np and pp interactions are the same, charge symmetry states that the nn and pp interactions are equal. The latt_er approximate symmetry is experimentally verified by the comparison of the excited levels lying at about the same energy in light mirror nuclei. Both of these symmetries are broken by the electromagnetic interaction. The neutron facility at the University of Kentucky provides a unique opportunity to examine charge independence, and in particular, charge symmetry from the reduced electromagnetic transition probabilities and neutron scattering cross sections. Here, we use the isospin formalism by Bernstein, Brown and Madsen, which relates the proton and neutron matrix elements, M p and M n respectively, for equivalent excited states in T=1 mirror nuclei (Tz = +/−1). The nucleus 18O has been studied using the (n,n′) reaction in order to measure the neu...

Isospin purity in the A=42 isobars

The lifetime of the first 2T=1+ state in 42Sc has been measured as 74(16) fs. This result gives a value for the isoscalar matrix element of M0=6.63(76). From the mirror nuclei, 42Ca and 42Ti, the isoscalar matrix element is given as 7.15(48) W.u., confirming isospin purity in the A=42 isobars.